ED YONG: The following program is rated as SGM for science, genitalia, and microbes.

Viewer discretion is advised.

[music playing] ED YONG: Your first birthday may have looked something like this, not that you remember any of it.

That was the day you received you favorite rattle.

You loved that thing.

Oh, look, your first stuffed animal.

You may think that these were your first birthday presents, but actually, they weren't.

Your first presents were given to you much earlier on the very day you were born.

It wasn't your name, it wasn't the love of an adoring family.

It was microbes.

You were born slathered in your mother's micobes.

They were everywhere, all over you.

MARIA GLORIA DOMINGUEZ-BELLO: They're in every mucosa, the mouth, the skin, the gut, the nose.

These are microbial communities, and they are our first birthday present.

That's Maria Gloria Dominguez-Bello.

I'm an associate professor at NYU School of Medicine, and I work on babies.

Babies and bacteria, which might sound like an awful combination; but Gloria believes that those first microbes from mom are really important for the development of a strong immune system.

The bacteria that they baby encounters during labor before being born, those are the pioneer bacteria.

So here's how that first birthday present works.

The vagina, microbes number in their millions in here Oh, look there's you, barreling ahead head first.

If you were born vaginally, you were given a serious bath in mom's microbes.

GLORIA: It's like an earthquake to have a baby, the squeezing, the work.

ED: Microbes are going into your eyes, your nose, your mouth, with each swallow, new microbes going right into your gut.

By this time your umbilical cord is cut, that microbial bath is seeping into every one of your orifices.

These microbes are the founders of the rich community of organisms that live on and in the body, what we call the microbiome.

When an infant is born, it still has a lot of developing to do.

Its environment and its diet help to shape its process.

But so do its microbes.

We're starting to discover that microbes play a really important role in those critical early months, and they help to shape the immune system so it functions properly throughout the rest of our lives.

So what happens if we miss that first microbial bath, that first birthday present?

What happens if we're born by a C-section?

In cesarean section, or C-section, the fetus is removed through an incision in the mother's abdomen and uterus.

This method has been practiced for thousands of years.

Today, nearly a third of babies in the US are born through C-sections.

It's often used when the fetus is sideways, or if it's in distress, if the mother is experiencing medical complications, or if the fetus is just too darn big.

The C-section can also be used for the sake of convenience.

Unfortunately for moms, labor takes hours.

Those hours of labor, the baby already gets exposed to our flora from the vaginal canal.

That doesn't happen in C-section.

ED: So with a C-section, the vaginal microbes are missing, and environmental microbes take their place.

So the question is, does that matter for babies?

The effect on microbes is proven.

ED: So babies born through C-sections definitely have different microbes than those born vaginally?

GLORIA: Exactly.

What is now proving is the effect, the effect on health of the baby.

When babies are not exposed to the natural, primordial, microbial-- I call it yogurt.

When babies are not exposed to this primordial soup of microbes, we think there are consequences, such as increased risk of obesity, or increase the risk of asthma, type one diabetes, celiac disease.

There's some evidence that babies born through C-sections have a higher risk of allergies and other health conditions.

So Gloria is studying those babies to better understand the potential consequences of bypassing the birth canal and being deprived of that first microbial bath.

So how do you do that?

You can't just go back in time and deliver the baby in a different way.

GLORIA: We cannot restore labor, but can we restore the microbes that happened naturally?

So Gloria designed an experiment to answer that question.

GLORIA: We had a pilot study in which the 18 first babies, seven born vaginally, seven born by C-section with no exposure, and four born by C-section and exposed to the maternal vaginal fluids.

Wait, how do you do that?

How do you expose a C-section baby to mom's vaginal fluids?

To do that, we have used a swab that we fold like a tampon, place it in the vaginal canal before the C-section.

When the baby is born, first thing is to clean, swab this baby with a gauze.

OK, I've got this.

So gauze, we take the gauze, and we fold it up, fluids from mom, baby, and we swab the baby, swab, swab, swab, swab, swab, swab, swab, swab, and tada, one baby completely covered in mom's microbes.

And how soon after it's born do you do that?

GLORIA: As soon as possible, within the first two minutes.

So question, when you were trying to get parents involved in this, were they like, you want to do what with my baby?

Exactly.

The first time was like, what's the rationale?

Why would you give microbes to a baby?

But then once you explain, it's reasonable.

It's a natural exposure.

What we want to understand is will the babies that are born by C-section and are exposed to their mother's vaginal fluids be colonized by the vaginal bacteria as if they were born vaginally?

So what happened in the end?

What were the results?

We follow those babies for the first month and compare them.

And what we found is that the babies born by C-section with exposure to the vaginal gauze, you see vaginal microbes as if the baby was born vaginally.

Huh, so the swabbing was enough to give the babies their microbial birthright?

Yes.

So this sounds very simple, but I'm guessing you're going to tell us that you shouldn't do this at home.

You should not do it yourself alone without the knowledge, because infections could be transmitted.

So what's next?

Are you going to do a bigger study beyond just the 18 babies?

GLORIA: We did it.

We continued it to 84.

And we are now analyzing massive, massive, data.

It's over 10,000 samples that we are analyzing right now the results.

But here's the thing, other large studies have found that if you look at children later on in life who were born either vaginally or through C-sections, you don't see any differences in their microbiomes anymore.

They start to look the same after awhile.

So the question is, would normalizing the microbes to mimic a vaginal birth at this early point in life reduce the risk of disease later on?

That is what Gloria wants to find out.

That's correct.

We know that we are restoring the microbes.

But what we don't know is are we protecting them from the increased risks that they had because they were born by C-section?

That, we don't know.

And that takes a long study, big, and long study.

What should people take away from this research?

GLORIA: The point is, C-sections save lives.

We know that.

So what is important to consider is that it's not free.

There is a price to pay.

But through your work, you're hoping to minimize that price.

I think in principle, we can restore nature through replacing the microbes.

So that however you come into this world, you've got the best possible chance for a healthy start.

That's correct.

Thank you, Gloria, for helping us to see the process of birth in a whole new light.

You're welcome.

And now, if you'll excuse me, it's nap time.