AMNA NAWAZ: Good evening.

I'm Amna Nawaz.

Geoff Bennett is away.

On the "NewsHour" tonight: The world records the hottest average temperature ever, while raging Canadian wildfires highlight the devastating effects of climate change.

Facebook's parent company, Meta, launches a competitor to Twitter, as the two companies' leaders intensify their rivalry.

And a group of Ukrainian mothers go to extreme lengths to rescue their kidnapped children from territory occupied by Russian forces.

JANNA, Ukrainian Mother (through translator): I haven't seen my daughter for more than five months, since the children were sent to the camp.

My only dream is to spend time with her, cherish her, love her, protect her.

(BREAK) AMNA NAWAZ: Welcome to the "NewsHour."

It has been a week of record-breaking heat around the world.

The average global temperature on Wednesday hit 62.9 degrees Fahrenheit.

According to researchers at the University of Maine, that matched the unofficial record-high just set on Tuesday.

The grim milestones are the latest in a series of climate-change-driven extremes.

Out-of-control wildfires in Canada have burned millions of acres, displaced tens of thousands of people, and blanketed wide swathes of the U.S. in thick smoke.

For more on all these events and what we should take from them, we're joined by Mike Flannigan, an expert on climate change and wildfires at Thompson Rivers University in British Columbia.

Professor Flannigan, thanks for joining us.

This week, we saw the hottest global temperatures ever recorded.

That is since tracking began in 1979.

What does that tell us?

And how concerning is that to you?

MIKE FLANNIGAN, Thompson Rivers University: It's very concerning.

We're in uncharted territory.

And we jumped up 0.3 degrees Fahrenheit.

That may not sound like much, but, compared to our record, that's sticking out like a sore thumb.

So we're in uncharted territory.

We can expect more record-breaking heat, as El Nino builds in.

AMNA NAWAZ: Scientific models have, of course, been predicting a warming climate for some time.

But did we expect to see these kinds of temperatures this soon?

MIKE FLANNIGAN: I would say our models on temperature have been pretty good.

Where we have fallen short is on impacts.

We're seeing much more impacts from our warming climate than what we expected.

And the impacts are only going to get worse and worse.

AMNA NAWAZ: Tell me more about what you mean by impacts.

MIKE FLANNIGAN: So, I study forest fires, and I have been studying forest fires since the 1970s.

And I have never seen a year like we're seeing in Canada this year.

This is exceptional, extreme.

And we're into new territory.

We have burned almost nine million hectares, and that's bigger than the state of South Carolina.

And these fires will continue to burn through the summer, and they will generate smoke that can impact tens of millions of people.

If you live in downtown New York City, the likelihood of your place burning down is essentially zero.

But you can be smoked out for weeks from a fire that's 1,000 miles away from New York City.

AMNA NAWAZ: Professor Flannigan, of course, we have seen the impact of those fires, as you mentioned down here in the U.S. And when you look at a chart, you can see just how much more total area has been burned this year in those Canadian wildfires -- that's the red line on top -- as compared to years past.

But help us understand how climate change is part of the conversation and driving these record fires you're seeing.

MIKE FLANNIGAN: So, as the climate warms, we're seeing more and more fire.

And people ask me all the time, why is temperature so important?

Well, it's because we're getting a longer fire season with that warming.

We're getting more lightning-caused fires with that warming.

And lightning-caused fires are responsible for most of the burned area in Canada.

Also, as we warm, it dries out the fuels, and drier fuels means it's easier for a fire to start, easier for a fire to spread.

And it means the fires have more fuel to burn, which means that leads to a higher-intensity fire, which can be difficult to impossible to extinguish.

AMNA NAWAZ: We have seen in the latest maps showing there are still hundreds of fires burning out of control across Canada.

Those are indicated by the red dots you see here.

What's key to making sure that these fires don't end up devastating communities And how would you say Canada is doing on that front?

MIKE FLANNIGAN: There's a lot of year-to-year variability in fire because of the weather.

We have seen extreme fire weather very early on in the season going right through the season so far, from sea to sea to sea.

We already have broken the previous record for area burned, and we still have much the fire season ahead of us.

AMNA NAWAZ: Professor Flannigan, I have to ask you the question we often hear when reporting on issues around climate change, which is this idea that the Earth has gone through heating and cooling periods over its entire existence.

How do you know this isn't part of some larger cyclical pattern?

MIKE FLANNIGAN: Well, if we were following the natural cyclical pattern, we would be into a cooling stage.

But we're going the opposite direction.

We are warming.

We have the greenhouse gases that we know, like carbon dioxide, since the 1950s going up and up to levels we have not seen for three to four million years.

And these are the primary reason why we are warming, because of human activities.

AMNA NAWAZ: Finally, when we look at the record wildfires in Canada, are those indicative of what other areas that regularly see wildfires, like California, for example, what they should expect ahead?

MIKE FLANNIGAN: In the future, as our world warms, we're going to see more and more fire.

And this applies to Canada and the United States and Australia.

And there's three ingredients for wildfire.

It's a simple recipe.

You need vegetation.

We call it fuel.

How much, how dry, important.

Second, ignition, people and the lightning, and, third, hot, dry, windy weather.

As we move into the future, we're seeing and we expect more hot, dry, windy weather in Canada, Western United States.

Western United States has already seen an increase of four times in terms of area burned since the 1970s.

In Canada, it's a doubling.

So the impact has already been greater in Western United States than Canada, but we're following the same path.

AMNA NAWAZ: That is Professor Mike Flannigan from Thompson Rivers University in British Columbia joining us tonight.

Professor, thank you for your time.

MIKE FLANNIGAN: My pleasure.

AMNA NAWAZ: In the day's other headlines: Russia staged its heaviest strike yet on civilian areas of Lviv in Western Ukraine, killing at least five people.

Cruise missiles hit an apartment building in Lviv, just 43 miles from the Polish border and far from the eastern front.

Drone footage showed the roof blown off the apartment block and the top floors destroyed.

Residents watched from the ground as rescuers worked to clear the rubble.

There's word that Russian mercenary leader Yevgeny Prigozhin is in Russia after all.

He staged a short-lived rebellion last month, before the president of neighboring Belarus, Alexander Lukashenko, negotiated a deal to take him in.

But, today, Lukashenko made comments that raised new questions about that deal.

ALEXANDER LUKASHENKO, President of Belarus (through translator): As for Yevgeny Prigozhin, he is in St. Petersburg.

Where is he this morning?

He might travel to Moscow or he might be elsewhere, but he's not on Belarus' territory.

AMNA NAWAZ: Its unclear if Prigozhin would be violating the terms of his agreement if he is in Russia.

The Kremlin today had no comment on his whereabouts.

A toxic gas leak in South Africa killed 17 people, including three children, last night at a settlement outside Johannesburg.

Today, police removed large canisters filled with nitrate gas from the site.

They blamed an illegal gold processing operation for a tragedy that shocked local residents.

NYAMEKA THWESHA, South African Resident (through translator): We knew that illegal miners used generators in their trade.

We had no idea that they also used gas, so we never expected something like this to happen.

This has affected everybody in a big way because innocent people lost their lives.

AMNA NAWAZ: Makeshift gold mining and processing is a dangerous, yet common operation in the deeply impoverished settlements around Johannesburg.

Back in this country, former President Trump's valet pleaded not guilty today to helping hide classified documents.

Walt Nauta left the federal courthouse in Miami after an arraignment that lasted just a few minutes.

He did not speak to reporters.

Prosecutors say Nauta moved boxes of documents before a search of Mr. Trump's Mar-a-Lago home and then lied about it.

The Food and Drug Administration has fully approved the first drug to slow cognitive decline in the early stages of Alzheimer's disease.

Today's endorsement of Leqembi opens the way for Medicare and other insurance to pay for the Japanese-made drug.

A large-scale study showed it can slow memory and thinking decline by five months in Alzheimer's patients.

And, on Wall Street, stronger-than-expected jobs data prompted concerns that it will take even more interest rate hikes to slow the economy.

The Dow Jones industrial average lost 366 points, or 1 percent, to close at 33922.

The Nasdaq fell 112 points.

The S&P 500 was down 35.

Still to come on the "NewsHour": residents in the West Bank struggle to recover from an Israeli military operation; a Republican senator blocks confirmation of military posts over abortion policy; the FDA clears a drug that could help pregnant women gauge their risk of a dangerous condition; conservationists work to bolster the dwindling population of northern right whales.

Mark Zuckerberg's company Meta has launched its new app that's expected to compete with Twitter, which has faced backlash under the ownership of Elon Musk.

The text-based app, known as Threads, looks nearly identical to Twitter and has seen more than 30 million users sign up since yesterday's launch.

Mike Isaac is a technology reporter for The New York Times, and he has been covering it all.

Mike, welcome, and thanks for joining us.

Thirty million sign-ups as of noon today.

Was that to be expected or does that number surprise you?

MIKE ISAAC, The New York Times: It certainly surprised me.

It's even really surprised Mark Zuckerberg, who woke up this morning and around 8:00 a.m. posted 30 million.

And last night he was posting every couple of hours basically as the numbers of users ticked up.

So, I think, even inside of Instagram, Facebook, and Meta, they're really surprised at how quickly people are embracing the app.

AMNA NAWAZ: So I think you have been testing out the new app, as have I, many other people too.

What do you think?

How is Threads going to compete with Twitter?

MIKE ISAAC: Yes, I mean, the sort of simplicity of it, in that it is basically the exact same thing as Twitter, I think, really helps the product, just because folks have been really upset by a lot of the changes that Elon Musk has made to Twitter since he bought it last year.

And they basically wanted another Twitter, but not owned by Elon Musk.

And this also lets you import the graph of people that you follow on Instagram over to the new app, which basically makes it up -- make it easy to get up and going right away instead, of having to follow a bunch of people right off the bat.

AMNA NAWAZ: And the functionality is basically the same, right?

It's text-based.

You still have a scrolling feed.

You can post videos and pictures too.

But what about the timing, Mike?

Why now?

Why is Mark Zuckerberg going into Twitter's territory right now?

MIKE ISAAC: Sure.

Frankly, I think it's because Mark senses weakness.

And there is weakness.

Since Elon Musk took over Twitter, he's made a number of strategic and business missteps.

Last weekend, over the long holiday weekend, he took Twitter offline for a lot of people and basically the app stopped working.

And we were talking to the head of Instagram yesterday.

And our reporting basically said that they started developing the app inside of Meta last winter, when they saw that Twitter was really in tumult.

And Facebook and Mark Zuckerberg are intensely competitive, and they want to gain as much territory as they can.

And they saw that Twitter gave them an opportunity to do so.

AMNA NAWAZ: So, in terms of a response from Elon Musk, there's some reporting that Twitter's threatening to now sue Meta over Threads, sending Zuckerberg a cease-and-desist letter.

We know Musk has been tweeting about this.

This afternoon, he tweeted this, saying: "Competition is fine.

Cheating is not."

Mike, what is all this tell you about how Elon Musk views this competitor?

(LAUGHTER) MIKE ISAAC: He is not happy, for sure.

He has been basically pushing back, trying to get folks who are -- quote unquote -- "scraping" Twitter's data or using it to build other apps and services.

And I would take the threat of legal action pretty real from him.

He likes going to court and using his advantage in having billions of dollars to tangle things up in litigation is a real thing.

That said, he has a pretty formidable opponent in Meta and Facebook, which has also got very deep pockets and is willing to go to battle over this, as they said before, that the suit, they believe, is baseless.

AMNA NAWAZ: You cannot separate these apps from the men in charge.

You have two tech giants here and Mark Zuckerberg and Elon Musk.

They have engaged, as you mentioned, in their own personal feud online, even threatening to physically fight one another.

How does all of this competition factor into these business decisions right now?

MIKE ISAAC: No, you're exactly right.

I think just as much egos involved as there is business strategy, but I do think that we're in a really interesting and difficult time in social media.

And there was an assumption for a long time that Facebook kind of owned at all, but it feels more up for grabs in a lot of ways.

That probably wasn't true a few years ago.

So, you see Twitter sort of on the ropes, Meta creating new apps, different start-ups, like Bluesky, Mastodon, Spill.

There's a bunch of different companies that feel like there's an opportunity here.

And at the helm of almost all of these, you have either the billionaires of the world controlling them or would-be entrants from little start-ups that feel like they can break in from, like, BeReal, which is another one.

So everything feels very up for grabs and up in the air in a way that that's pretty exciting and hasn't been like this in a while.

AMNA NAWAZ: We will see what happens next.

That is Mike Isaac, technology reporter from The New York Times, joining us tonight.

Mike, thank you.

Good to see you.

MIKE ISAAC: Thanks for having me.

AMNA NAWAZ: For the first time in over a century, the U.S. Marine Corps will not have a permanent leader.

Current Marine Corps Commandant David Berger is in his last week on the job.

He's required to retire on Monday.

But due to a hold on hundreds of military promotions by Alabama Senator Tommy Tuberville, there's no confirmed replacement.

If this continues, other branches will soon have the same problem.

To help unpack the standoff, I'm joined by congressional correspondent Lisa Desjardins.

Lisa, good to see you.

LISA DESJARDINS: You too.

AMNA NAWAZ: So, remind, us, what is the senator doing here and why?

LISA DESJARDINS: The senator is flexing the power, unique power, of an individual senator to affect the time on the floor, and he is blocking 250 now military promotions.

These are senior-level officers, flag officers.

Think generals and admirals, by and large.

Now, the issue is, of course, why is he doing this?

Why is he slowing down these nominations?

It's about abortion.

Senator Tuberville objects to the now defense policy put in place after the end of Roe v. Wade, in which the Defense Department will pay for travel for a service member to get an elective abortion if there's not one available where they are based.

And Tuberville says that is the issue here.

SEN. TOMMY TUBERVILLE (R-AL): These holds have no real impact on military readiness or operations.

The military wasting time and resources to coordinate abortion trips hurts readiness, not the Senate using regular order to vote on nominees.

LISA DESJARDINS: Now, sources close to Tuberville tell me he's also unhappy because Defense Secretary Austin only called him once.

Tuberville feels like he warned that he might do this.

He wants more engagement.

But those around the defense secretary, the military, say he's not going to negotiate, nor should any defense secretary, with a single senator over their policy.

So, quickly, let's look at where we are in what's ahead in the next couple of weeks.

So, as you just reported, the commandant of the Marine Corps retires on Monday, but that's not the only one coming.

In August, near the beginning of August, the Army chief of staff will retire first.

Then, shortly after that, the chief of Naval operations also due to retire.

Then, followed in October, the very top military officer in our nation, the chair of the Joint Chiefs of Staff, set to retire.

With no confirmed replacements, Amna, all of those positions will be filled by acting officers.

AMNA NAWAZ: So, Lisa, we heard the senator there saying he doesn't believe there's any impact to his actions here.

What about the military?

What are they saying?

LISA DESJARDINS: Could not disagree more.

They think this is dangerous.

No one thinks the Marine Corps or the military will collapse at having acting commanders here.

But when you talk to those who cover it, you find that there are some ripple effects already.

For example, we talked to Rebecca Kheel.

She's a reporter who covers the military.

REBECCA KHEEL, Military.com: They very much think it is a big deal.

This is going to be the first time in more than a century that the Marines have had an acting commandant.

So, it is -- it's not unprecedented, but it is very rare.

And, like, with that leadership vacuum, and not being able to make these big strategic decisions at a time we're facing the war in Ukraine, and we're trying to prepare for any conflict with China, not being able to make those long-term big planning decisions is going to affect the military.

LISA DESJARDINS: An acting commandant, for example, couldn't make decisions on the fly.

They would have to stick with whatever decisions are in place now.

And as you just heard, we know this is a world that's changing quickly, China, Ukraine, major pressures going on.

Also, in addition to this, families of these officers will not be able to move.

This is a time right now, the summer, when usually families are moving so their kids can start school in the fall, hundreds of families at risk there for that kind of issue.

And in addition to that, we also know that what's happening is some lower-ranking officers - - I talked to one today -- are thinking, maybe I don't even want to go for the promotion if this is going to be a political world.

I also spoke to one former chairman of the Joint Chiefs of Staff.

That's Admiral Mike Mullen.

And he said very clearly: "Senator Tuberville is saying he supports the military, but he's having the exact opposite effect."

AMNA NAWAZ: Lisa, to be clear here.

Senator Tuberville is the only one involved in this hold, right?

So how much pressure are others, especially other Republicans, putting on him to reverse course here?

LISA DESJARDINS: When this first started back in March, I think we expected pressure to mount pretty quickly.

But the truth is, he doesn't really feel much pressure from Republicans at all.

There is one Republican who has kind of openly and very clearly opposed what he's doing.

It's a big one, Senator Mitch McConnell.

Here's what he said about this in May.

SEN. MITCH MCCONNELL (R-KY): No, I don't support putting a hold on military nominations.

I don't support that.

But as to why, you need to ask Senator Tuberville.

LISA DESJARDINS: Behind the scenes, there's a strange lack of engagement among Republicans.

They obviously are hearing from military officers.

Many of them feel that this has to change.

But there really isn't pressure on Tuberville at this moment.

In fact, it's the opposite, folks around him saying his constituents like what he's doing.

AMNA NAWAZ: So with all the concerns about leadership vacuums, and so on, how does this end and when?

LISA DESJARDINS: I have to say it's not clear.

There was a chance that this could become part of a defense authorization bill moving right now, but that does not look like this will be part of an off-ramp in that way.

Now, those around Tuberville say, hey, Democrats just have to take longer to do this, run the clocks, hours and hours for each nomination.

That would take months and months.

They're not going to do that.

And it sets a terrible precedent.

There are others who say call his bluff.

Make him stand in the Senate chamber and object to each of these nominations, also a bad precedent.

So I think the truth of it is, Amna, that this is going to be with us for a few months.

The Biden administration will try and pressure with things like maybe appropriations or military base things that he wants, but, right now, we don't know how this ends.

AMNA NAWAZ: You will be tracking it all, I'm sure.

Our congressional correspondent, Lisa Desjardins, thank you.

LISA DESJARDINS: You're welcome.

AMNA NAWAZ: The United Nations secretary-general today denounced what he called an excessive use of force by Israel in the occupied West Bank.

It comes after the Israel Defense Forces conducted a two-day operation in the Jenin refugee camp that it said targeted Palestinian militants.

Elsewhere today in the West Bank, an Israeli soldier was shot and killed by a Hamas militants near in Israeli settlement.

The shooter was then killed by Israeli forces.

As special correspondent Leila Molana-Allen reports from Jenin, the destruction after the fighting is massive, and the anger boiling.

LEILA MOLANA-ALLEN: In the blistering morning heat, the residents of Jenin camp are all hands on deck to clear the aftermath of this week's attack.

The air is clogged with dust, as chunks of asphalt, shattered glass and crumpled metal are swept aside.

Major infrastructure lies in pieces.

Burnt-out cars sit scattered on the streets outside homes bearing bitter pleas: "Everything we have is destroyed.

Please send us help."

Mahmoud Aljul (ph) had sensed something was coming.

Several days before the operation, three of his adult sons were arrested after an Israel Defense Forces raid on his house while they had breakfast.

MAN (through translator): They raided the village.

They came to my house, they blindfolded my boys, and they took them away.

LEILA MOLANA-ALLEN: Mahmoud says his sons have done nothing wrong.

With many young men in the camp in favor of the Palestinian resistance to Israel's occupation of the West Bank, but not necessarily fighting, it's a gray area that's a common problem in terms of what the IDF considers adequate grounds for detention and interrogation.

With two sons still in custody, on Monday morning, missiles began to rain down around the family.

Like many others, they decided to flee as soon as they were allowed to leave.

When they returned two days later, it was to a scene of devastation.

MAN (through translator): This is a barbaric act.

Look what they have done.

They use the excuse that they're looking for someone.

But look at this.

Look at all the damage they have done.

LEILA MOLANA-ALLEN: Mahmoud's house was flattened in the 2002 operation here, during the height of the Second Intifada, or uprising, by Palestinians.

And the family had to rebuild from scratch.

Now they face another rebuild with their savings gone.

There is a huge amount of anger and resentment here, and that could still boil over.

But, today, right now, the priority is to get this place livable again as quickly as possible.

The main roads have been bulldozed to pieces.

The main water supply into town was hit, isn't functioning.

The main health care system was attacked, and that center is closed.

And people here really have nowhere else to go.

Israel's Prime Minister Benjamin Netanyahu hailed the operation as a resounding success Wednesday.

BENJAMIN NETANYAHU, Israeli Prime Minister: We operated in a very systemic way with large forces in one of the most concentrated and dense areas on the planet.

LEILA MOLANA-ALLEN: The scale of the operation, the most intense carried out in the West Bank in nearly two decades, was a significant escalation, with helicopter gunships, artillery and missile-carrying drones deployed in a dense area of less than half-a-square-mile, packed with up to 20,000 civilians at any one time.

U.N. experts said today the IDF's use of airstrikes and elite ground troops here may constitute war crimes.

Nine of the 12 dead Palestinians were claimed by militant groups as members.

But beyond the dead and injured, the sheer scale of destruction and injury here is a casualty in itself, lives uprooted and children traumatized in a place where it's already a struggle to survive.

Dana Dodeen from UNRWA, the U.N. agency that operates services for Palestinians here and in the 18 other camps across the country, who was here to survey the damage.

DANA DODEEN, UNRWA: So the work is ongoing.

We haven't stopped working since the beginning of this crisis.

And, yes, we're just hoping to resume to our operations.

Like, our first priority is to be able to open the school, having the children there as a safe -- safe space.

LEILA MOLANA-ALLEN: Donna, UNRWA is already struggling for money.

This year, you only have $100 million of the $300 million that you need.

That's a two-thirds shortfall.

And that was before this situation.

By having to constantly rebuild these camps that you run when they're damaged, how does that affect your ability to provide the everyday services like health care and education that you have to provide for people here?

DANA DODEEN: Well, of course, the need is dire.

And, yes, we are counting on the support of the international community, as always.

LEILA MOLANA-ALLEN: It's not just homes, but families and livelihoods that have been torn apart throughout the tight alleys of the camp.

Jihad Mohammad Yassin's son was badly injured by a rocket in the early hours of Monday's assault.

JIHAD MOHAMMAD YASSIN, Jenin Resident (through translator): I carried him in my arms and walk searching because no one could reach us.

I was so lucky I found an ambulance to take him.

LEILA MOLANA-ALLEN: In the 2002 assault on Jenin camp, Jihad's left leg was nearly destroyed by an incoming missile.

On Monday, his son was injured in the right leg standing in nearly the same spot by a similar weapon.

On Monday morning, during the assault, a rocket came in through this window and injured his son; 20 years ago, a rocket came through the same window injuring him history, repeating itself in this family.

Jihad returned from the hospital to find his small butcher's shop, the family's only reliable income, in pieces.

Not only the military operation, but the street-to-street gun battles that followed, destroyed shops on the main drags throughout the camp.

JIHAD MOHAMMAD YASSIN (through translator): Is my shop a terrorist?

No, Israel's the main terrorist.

LEILA MOLANA-ALLEN: Jihad's mother, Aida, originally comes from Haifa on the Mediterranean coast and settled in Jenin camp after her entire family was killed by an IDF missile during the 1967 war.

She worked for 30 years to build this house, rubbing away the very pigment from her skin through years of hard labor in a cement factory.

AIDA, Mother of Jihad (through translator): We left our home in Haifa, and now they're chasing us here.

Why are they still going after us here?

LEILA MOLANA-ALLEN: Now, at 93 years old, it's time for her to rebuild her home a third time.

I haven't seen a hospital in Jenin town, where the most injured were rushed when the blockade allowed.

The blood has been washed from the floors and calm restored.

Operations for the most serious injuries are under way.

In a bed upstairs, Jihad's 21-year-old son lies recovering from surgery that reconstructed his lower leg bones with a 15-inch titanium rod.

JIHAD MOHAMMAD YASSIN (through translator): The shrapnel from a missile hit my son in the leg.

The force of the missile lifted him three meters off the ground and threw him back down.

Now I don't know how long it will take him to heal, and he won't be able to work for a while.

He's in a paralyzed situation.

LEILA MOLANA-ALLEN: Jihad's son is too afraid to show his face or speak to us.

Traumatized and injured, he fears reprisals from the IDF if he's identified.

JIHAD MOHAMMAD YASSIN (through translator): The pain I felt 20 years ago, he's feeling it now.

LEILA MOLANA-ALLEN: Like so many others here, Jihad, exhausted and afraid, must now piece back together his home, his family and his livelihood, never knowing when destruction may come knocking again.

For the "PBS NewsHour," I'm Leila Molana-Allen in Jenin camp, the West Bank.

AMNA NAWAZ: The Food and Drug Administration has approved a blood test that can identify pregnant women at severe risk for preeclampsia, a high blood pressure disorder that can develop during pregnancy.

As Stephanie Sy reports, the condition is a leading cause of maternal deaths worldwide.

STEPHANIE SY: Roughly one in 25 pregnancies in the U.S. is affected by preeclampsia, according to the Centers for Disease Control and Prevention.

If undetected and untreated, severe preeclampsia can cause maternal death.

In recent years, the condition accounted for about 6 percent of total maternal deaths in the U.S. Dr. Ravi Thadhani is executive vice president for health affairs at Emory University and co-author of a study that looked at this blood test.

Dr. Thadhani, thank you so much for joining the "NewsHour."

I understand there are already a variety of tests to check if a pregnant woman may have preeclampsia.

So what is different or better about this blood test?

DR. RAVI THADHANI, Executive Vice President For Health Affairs, Emory University: Stephanie, thank you for the question.

Preeclampsia is a hard condition to diagnose, but it's an even more difficult condition to predict.

This is the first test approved by the FDA to predict this terrible condition.

Importantly, it adds to a toolkit of other tests and measures that clinicians use.

We use blood pressure and a variety of blood tests.

But this particular test adds precision to the diagnosis and prediction of preeclampsia.

There are two important features of this test.

One is, it actually yields information before a woman actually gets sick.

So, as a prediction, it does really well.

And, secondly, it acts like a time clock, like a countdown, and tells you when she's going to get sick.

STEPHANIE SY: It is a terrible condition.

In fact, many of us will have heard of Tori Bowie, that track star who died just a month ago in childbirth.

She is believed to have had eclampsia at the time of her death, which really put a spotlight on this condition.

She was obviously very fit, as is former track star Allyson Felix, who also had preeclampsia during her pregnancy.

What does this tell us about who is at risk for this condition?

DR. RAVI THADHANI: Preeclampsia happens in about 5 to 7 percent of all women who get pregnant in the United States.

That's about 200,000 women.

Most preeclampsia happens at term, where it's mild.

It's really the preterm preeclampsia that we focus on, because, a woman, if she delivers preterm, the risks for the baby, of course, are incredibly high.

The only treatment we have for this condition is the delivery.

We know and understand some risk factors for this condition, Stephanie, high blood pressure, obesity, diabetes, in vitro fertilization, and so forth.

But we truly don't know the cause of this condition.

We have a better understanding of the biology as to who gets the condition.

The women that you mentioned, incredibly unfortunate.

We know that the condition affects Black woman at a rate of three to five times higher than women who are non-Black.

And while we don't understand why that's the case, we have a better understanding, like I said, of the disease overall.

And this test, of course, helps us with that.

STEPHANIE SY: Yes, I was going to ask who this test was for and whether you see this test as becoming something in routine pregnancy screening, and whether all women will have access to this blood test.

DR. RAVI THADHANI: So, what we did in this study, Stephanie, is, we studied women who came in to the hospital with high blood pressure.

So, clearly, they had some risk factor already.

And we used the test to predict -- or at least the test was able to predict who went on to get severe -- severe disease.

The risk factors, as I mentioned, high blood pressure, diabetes, in vitro fertilization, twin pregnancies, one can imagine the test first focused on those women with those risk factors.

But, unfortunately, there are women without any risk factors.

In fact, that represents the majority of women that get this condition.

And, again, we still don't understand why or when they get the condition.

As far as screening or routine use of this test, right now, it's only, I believe, going to be used in women at high risk for the condition.

STEPHANIE SY: And I understand that this test is already in use in Europe.

How widely might we see it be in use here in the U.S., where we have an extremely high maternal mortality rate, among the highest among developing nations?

DR. RAVI THADHANI: Yes, that's right.

Unfortunately, we have some of the highest maternal mortality rates.

I currently work in Georgia, and it ranks among the top states, but also in other parts of this country.

Really unfortunate.

The test is actually available in a few sites now.

And, certainly, as we roll into the summer and into the fall, the test will become much more widely available.

We have used this test in Europe, not by way of a full approval, but a conditional approval in Europe, and people use it and find it incredibly useful.

This, of course, represents the largest study that we have completed in the United States, demonstrating that the test has utility in the diversity of women that get pregnant and give birth here.

STEPHANIE SY: Well, it is certainly a toolkit that needs more tools to address maternal mortality.

Dr. Ravi Thadhani with Emory University, thanks so much for joining us with your expertise.

DR. RAVI THADHANI: Thank you, Stephanie.

AMNA NAWAZ: Nearly 20,000 Ukrainian children have been unlawfully transferred to Russia or Russian-controlled territories of Ukraine since the war began nearly a year-and-a-half ago.

International arrest warrants have been issued for Russian President Vladimir Putin and another member of his government for those crimes, but mothers and grandmothers have also taken matters into their own hands.

With the support of the Pulitzer Center, filmmakers Amanda Bailly and Anton Shtuka bring us the stories of the fierce women who went to take back their children.

Special correspondent Jane Ferguson narrates their journey.

JANE FERGUSON: Of all the civilians to pass through Kyiv train station in this war, few have more at stake than these women.

They have just arrived from areas in Ukraine once occupied by Russian forces.

They are on a journey to get their children back.

JANNA, Ukrainian Mother (through translator): I haven't seen my daughter for more than five months, since the children were sent to the camp.

My only dream is to spend time with her, cherish her, love her, protect her.

JANE FERGUSON: Each woman on this bus has a similar story.

They bond quickly, having shared the same horror.

Now they share the same mission.

Janna's daughter Masha is in the Russian-controlled Ukrainian territory of Crimea.

Masha is a vibrant, sporty 13-year-old.

When the Russian forces took over their home city, Kherson, just to the north of Crimea, Masha's school told Janna the area was not safe for children due to Ukrainian shelling.

They planned to move the kids to facilities that were summer campgrounds for Ukrainian children before the war, only, those camps were in areas now controlled by Russian military.

JANNA (through translator): They sent her to Mechta camp in Yevpatoriya, Crimea.

Masha is very good-natured and affectionate, but she's a fighter.

She's a professional-level karate fighter.

My girl is very active and sociable, loves playing with children and babies, and loves to spend time with her friends.

JANE FERGUSON: Janna says the authorities at Masha's school pressured her to send Masha, promising her in writing she would be back in two weeks.

JANNA (through translator): They offered it for safety reasons.

They told us that fighting in the city would start soon, and it would not be safe for children to be in the city, and that schools are shelled by the armed forces of Ukraine.

So we were offered to send them to Crimea so that the children could rest and continue school.

They promised to bring the children back in two weeks.

Well, no one brought anyone back.

JANE FERGUSON: Janna said the Russian authorities told parents, after one month, they could come and collect their children, but would have to stay in Russian-controlled territory with them.

But crossing the front lines and returning is near impossible.

At the same time, the Russian authorities were easing regulations for Russian families to adopt deported Ukrainian children like Masha and raise them as Russians.

Ukraine says at least 19,000 Ukrainian children were moved by the Russian military and collaborators into Russian-controlled territories since the war began.

Natalia is from Kupiansk in the east.

When Russian soldiers and local collaborators retreated from the town, to her horror, they took her 15-year-old son, Artem, with them.

NATALIA, Ukrainian Mother (through translator): On September 7, he went to school.

He stayed the night at the school, as there was no bus home in the evening.

And in the morning, those people, I don't know how to call them, took kids with them when they were running away from Kupiansk.

They took 13 kids with them.

How did this happen?

And we had no electricity and mobile connection at that time.

We were looking for him.

We were in a panic.

JANE FERGUSON: Artem was taken to a school in Luhansk, a Russian-controlled area in Ukraine.

After a month with no word, he was finally able to make contact with his terrified mother.

NATALIA (through translator): It's good that Artem knew my number from memory, and he took a phone from the principal of the school where he is now, called me on WhatsApp, and told me where he was and what happened.

I have been waiting for half-a-year now.

JANE FERGUSON: As days turned to weeks, then months, it became increasingly clear the children had been taken for good.

NATALIA (through translator): These last months were shocking.

I can't think about anything, can't do anything.

Well, there is a mess in my head.

All kinds of thoughts in my mind.

Artem called and said they were told that, if there is combat activity there too, they will be taken to Russia.

And they also had air raid alerts and incoming strikes.

And they were told that, if it gets dangerous there, they will be taken to Russia.

I got into a panic again.

JANE FERGUSON: Once in Kyiv, they overnight, preparing themselves for the long trip ahead into Russian and Russian-held territory.

Their journey is being organized by Save Ukraine, a charity creating a network of allies for the women inside countries and territories where their children are held and from where they need to be saved.

Save Ukraine is the only organization offering real, tangible help to these women.

Myroslava Kharchenko, a lawyer working with Save Ukraine, preps the women for what's ahead.

Most of these women have never been abroad before.

MYROSLAVA KHARCHENKO, Attorney, Save Ukraine (through translator): The main rule is to listen to the drivers.

They know what to say.

Different borders, they pass differently.

It will not be easy.

It will be a very long journey and stressful.

You will be going through different countries and will spend time in the country of your aggressor.

Memorize your driver's phone number, because anything could happen.

JANE FERGUSON: Journalists Amanda Bailly and Anton Shtuka were able to exclusively travel with the mothers for part of the journey as they embarked on the mission to bring home their children.

Most of the women had been able to make patchy contact with their children in recent days, preparing them and telling them to be ready to leave soon.

Svetlana is grandmother and guardian to 13-year-old Nastya.

She joins Natalia and Janna on the journey, telling her granddaughter she is on her way.

SVETLANA, Ukrainian Mother (through translator): I talked to Nastya.

She was delighted, she broke into tears, and I heard her voice and started crying.

I said: "Nastya, it's you, I'm so happy to hear you.

I'm really excited.

I am going for you.

You wait."

She said: "OK. Granny, I'm waiting for you, I'm packing my suitcase now."

And she was crying.

I hadn't heard her voice in a long time.

JANE FERGUSON: On the journey, people on the inside will help them make their way to their children, a network of allies working with Save Ukraine, and providing logistics, perhaps parents themselves.

JANNA (through translator): We are so grateful to the people who help bring back Ukrainian children from these foreign territories.

Our deepest gratitude to them.

Perhaps we would not see our children again without their help.

JANE FERGUSON: As they set off, the women are hopeful.

In each of their minds, they dream of what they will do when they see their children again, and the lives they will try to give them after the war.

JANNA (through translator): First, I will not let her go.

I will kiss and hug her.

I will apologize for letting her go there, for letting her be in such an environment.

And then I will cook something delicious, like her favorite cake, and I will buy her lots of chocolates.

And, later, when she recovers a little, I will play sports with her.

We will ride bicycles and lead an active life, like we used to before the war.

SVETLANA (through translator): I have always believed it.

Yes, I was afraid that I might lose her.

Nevertheless, I had hope, hope that I would get her back.

And I prayed every day.

I prayed every night.

And I had a hope that, sooner or later, I would see the child at home.

NATALIA (through translator): I will just hug him.

I just want him to be with me, nothing else.

I don't want anything else.

The most important thing is to take him back.

And that's it.

We will celebrate when the war is over.

Now it is not the best time for celebrations.

I want him by my side.

JANE FERGUSON: The journey is a long one, from Kyiv to Chelm in Poland by train, from Chelm to Minsk City in Belarus by bus.

From Minsk, they fly to Moscow.

From there, they travel by bus and car to Russian-controlled areas of Ukraine.

Music has always played here on loudspeakers.

This evening, it is a famous song about returning to mothers.

As they set off, journalists could not follow them on that journey, but along the way the mothers would film themselves where they could and when it was safe.

Finally, they make it here.

This is the campground in Russian-occupied Crimea where their children are being held.

It appears there are no Russian military present, just civilians working there.

The children come running to their mothers they have not seen in months.

They were handed back to the mothers without resistance.

After months of cautious self-preservation came waves of emotion.

For these women, as with mothers across the world, there is no distance they would not travel to find their children and bring them home.

For the "PBS NewsHour," I'm Jane Ferguson.

AMNA NAWAZ: Tune in tomorrow for Jane's second report on how those rescued children are readjusting to life back at home in a war zone.

It's estimated there are fewer than 350 North Atlantic right whales remaining.

They are dying faster than they can reproduce, and its largely due to human causes.

With so few of the whales left, experts are closely monitoring for new offspring and, as science correspondent Miles O'Brien reports, working to keep this whale from extinction.

MILES O'BRIEN: It was a perfect April morning when we steamed out of Provincetown Harbor in Massachusetts.

Cape Cod Bay was glassy as a lake, the visibility unlimited, the right kind of day.

CHARLES "STORMY" MAYO, Co-Founder, Center for Coastal Studies: Now, if we find whales...

MILES O'BRIEN: I assume you're going to say, when we find whales.

CHARLES "STORMY" MAYO: We're always going fishing.

This is a fishing trip.

MILES O'BRIEN: Marine biologist Charles Stormy Mayo has been looking for right whales for the better part of 40 years.

He is co-founder of the Center for Coastal Studies, a nonprofit committed to saving the whales.

CHARLES "STORMY" MAYO: I have been on hundreds of cruises.

When the first right whale shows up, it's still pretty special.

These are very odd creatures, and they live a mysterious, but, from a human point of view, a very odd life.

MILES O'BRIEN: It was not long before we hit pay waters.

WOMAN: We're seeing at least one individual right up here at 290 degrees.

MILES O'BRIEN: Soon, there were feeding, or skimming, North Atlantic right whales all around us.

WOMAN: Wow, there's a whole patch of them.

There's like, a whole bunch, like at least four.

MILES O'BRIEN: About two dozen in all.

CHARLES "STORMY" MAYO: Is that calf trying to skim?

It's got its head out of water.

MILES O'BRIEN: A rare thrill in every sense.

North Atlantic right whales are critically endangered.

Scientists believe there are fewer than 350 individuals remaining.

CHARLES "STORMY" MAYO: The future of right whales is dire.

And it's dire because the very simple arithmetic of the right whales population is bad.

The mortality rate is outstripping the birth rate.

The arrow points to zero.

MILES O'BRIEN: The whales migrate along the North American East Coast between Canada to Florida.

Humans have made this an increasingly perilous gauntlet.

Ship strikes and entanglement with fishing gear are the leading causes of death.

Stormy Mayo's team is part of a multifaceted effort to document this demise, in hopes that it can be stemmed.

WOMAN: Runway 32, cleared for takeoff.

MAN: Cleared for takeoff, Runway 32.

MILES O'BRIEN: An aircraft chartered by New England Aquarium scientists flies 50 missions a year to help track the whales.

WOMAN: The humpbacks were at, like, the northern end of the line, and then the right whales were further out.

MILES O'BRIEN: The aquarium is curator of an extraordinary photographic catalog of right whales dating back more than 80 years.

It's a collaboration with researchers at various institutions that aim to collect every photograph taken of a North Atlantic right whale.

Whale biologist Philip Hamilton is a senior research scientist at the aquarium.

Individual whales are identifiable by experts, able to recognize the unique patterns created by lice that live on the whales heads and behind their blowholes.

You have been doing this for a number of years.

Can you spot individuals by sight pretty well?

PHILIP HAMILTON, New England Aquarium: Yes.

Yes.

MILES O'BRIEN: It's that obvious in some cases?

PHILIP HAMILTON: I realized at one point I think I probably recognized more whales on sight than I did people.

(LAUGHTER) MILES O'BRIEN: Over time, the images and the scars tell a grim forensic story.

PHILIP HAMILTON: Once we realized that we are seeing this pattern of scarring from entanglements, and that's been an incredible wealth of information, able to track when and where right whales are becoming entangled.

MILES O'BRIEN: The whales move unpredictably.

This season, they gathered in Cape Cod Bay.

About half of the known population were here.

It turns out the place was brimming with their favorite food, a tiny shrimp-like plankton, a copepod, called Calanus finmarchicus.

CHRISTY HUDAK, Research Associate, Center for Coastal Studies: It looks like cinnamon applesauce.

(LAUGHTER) MILES O'BRIEN: Research associate Christy Hudak gathers plankton samples in the wake of whales to see exactly what they are eating, how much, and at what depth.

How does something so big subsist on something so small?

CHRISTY HUDAK: That is the ultimate question.

MILES O'BRIEN: Back in the lab in Provincetown, she carefully counts the plankton to determine their density and identify exactly what species the whales are favoring.

So, at this time of the year at least, Cape Cod bay is the ultimate right whale buffet?

CHARLES "STORMY" MAYO: It looks like it is.

The plankton that we collected today is an example.

It's unbelievably rich.

And these animals are consuming at very high levels.

Back-of-the-envelope calculation is, they may be taking over 125 pounds of plankton an hour.

MILES O'BRIEN: Unfortunately, their essential pursuit of plankton has led them to troubled waters.

Cape Cod Bay is part one of the fastest-warming ocean regions on the planet, the Gulf of Maine, and so the plankton picture is changing here.

It may be the reason the whales began altering their migration patterns in 2015, sending them into the Gulf of Saint Lawrence.

Scientists were caught off guard, and before they could suggest regulations to protect the whales in their new feeding area, a dozen were killed by ship strikes and entanglements with fishing gear.

This triggered an unusual mortality event.

Researchers have documented 36 right whale deaths and 62 injuries since 2017.

CHARLES "STORMY" MAYO: We have had several times of big mortalities of whales because they were entering an area where the managers had no idea that right whales were there.

But they came in probably searching for food in a changing environment.

MILES O'BRIEN: Given the onslaught they already face, climate could be the final straw?

CHARLES "STORMY" MAYO: Climate could be the final straw for all of us.

MILES O'BRIEN: There are solutions.

Ships can be rerouted or forced to slow down, and there is technology that makes it possible for fishermen to do their jobs without leaving vertical lines dangling in the water.

But this has put the desperate effort to save the whales on a collision course with one of the most lucrative fisheries in the world, Maine lobsters.

More on that soon when we continue our voyage.

For the "PBS NewsHour," I'm Miles O'Brien on Cape Cod Bay.

AMNA NAWAZ: And on the "PBS NewsHour" online, something to toast to, the scientific reason champagne bubbles rise in straight lines and why that's important to understanding other processes in nature and in medicine.

You can read more at PBS.org/NewsHour.

And that is the "NewsHour" for tonight.

I'm Amna Nawaz.

On behalf of the entire "NewsHour" team, thank you for joining us.