TOPICS > Health

In Vitro Risks

March 6, 2002 at 12:00 AM EDT


GWEN IFILL: Now, new research on the risks of in vitro fertilization. Two studies published today in the New England Journal of Medicine show that babies conceived through assisted means are more likely to be under weight and to suffer from birth defects. But how risky are these increasingly popular procedures? Here to tell us more about the new findings is NewsHour health correspondent Susan Dentzer. Our health unit is a partnership with the Henry J. Kaiser Family Foundation.

GWEN IFILL: So Susan, how dramatic are these findings today?

SUSAN DENTZER: Reasonably dramatic, Gwen. There’s been speculation for a long time and indeed studies for many years looking at the issue of increased birth defects and increased risk of low birth weight as a consequence of these assisted reproductive technologies. Studies have come out on various sides of that. What these studies appear to show with a reasonable degree of conclusiveness is that the risk of major birth defects is about twice as high for infants born through assisted reproductive means versus infants born in the general population. And the risk of low birth weight is also higher for infants again born primarily through in vitro fertilization and other assisted reproductive technologies.

GWEN IFILL: When you say assisted reproductive technologies, we’re talking about in vitro fertilization and what people commonly call test tube babies but it’s not really like that is it? There are other kinds of artificial ways.

SUSAN DENTZER: Yes. There are a range of additional measures that are undertaken. A common one that was also looked at in some of these studies is known as ICSI, it’s Intracytoplasmic Sperm Injection. It’s the primary treatment for male infertility. When a male has too low a sperm count or other sperm abnormalities one way to correct that is to go in, pick out a single sperm inject that right into the cytoplasm of an egg and achieve a pregnancy that way. That’s another technique that was included in these overall studies.

GWEN IFILL: So how popular, how widespread are using these techniques to get pregnant?

SUSAN DENTZER: The techniques have taken off in the last 15 years. We have a graphic I think that illustrates that. In 1985 basically 260 of these procedures were performed. In 1999, more than 30,000 babies were born as a consequence of these procedures. An IVF alone there are 45,000 infants born in the United States through in vitro fertilization at minimum to date. So these techniques have become very popular and will become more popular as they are perfected even more in the future. That’s why these studies do raise some concerns.

GWEN IFILL: Well, let’s talk about the concerns raised by the studies. Are women and their babies now at greater risk or have they always been at greater risk based on what these studies tell us today?

SUSAN DENTZER: Well, epidemiologists are always quick to point out the difference between what we call relative risks and absolute risks. If you step back and look at this, the absolute risks of have babies born with birth defects even through in vitro fertilization in a way are not all that great. More than 90 percent of the babies in the study that was done in Australia – that’s the study that looks specifically at birth defects — more than 90 percent of those babies born through in vitro fertilization and ICSI were fine.


SUSAN DENTZER: The Intracytoplasmic Sperm Injection that I mentioned a moment ago. Both of those techniques – you look at the babies born for them – more than 90 percent — 91 percent of those babies were fine. You look at the general population — 96 percent of babies born in the general population are going to be fine or certainly those that are born naturally and that were looked at in this study, the other group that was looked at in the study.

So the absolute risks are not that great and many fertility experts are quick to point out that if your choice between taking a gamble on having a child with a birth defect and you’re pretty confident that 90 percent of the time that’s not going to happen and this is your only way to have a child then you’re more likely than not to say let’s go ahead and take that gamble.

GWEN IFILL: Now, the second study was all about low birth weight. Why is it significant or a negative thing I suppose for children to be born with a low birth weight?

SUSAN DENTZER: Low birth weight is highly correlated with developmental disabilities and physical disabilities as well. It’s not always the case but there’s a higher incidence in those areas. So what this study did, this is the study by the Centers for Disease Control – it looked at populations again, babies who had been born through these treatments. An interesting thing emerged. There’s always been – it has always been known that these assisted techniques produced more multiple births, more twins and triplets and so on. That’s because lots of eggs are harvested.

Multiple embryos are transferred back into use so the incidents of these multiple births is higher. The issue has been is there really more of that that leads to low birth weight as a consequence of assisted reproductive technology. What this study said is interestingly enough if you’re a twin born through IVF versus a twin born normally you are no more likely to be lower birth weight. However, if you’re a single born infant born through IVF, you are more likely to be born low birth weight. In fact, you’re twice as likely to be born low birth weight, and this was the surprising finding out of this study.

GWEN IFILL: Now when we talk about defects, when we talk about low birth weights, what kind of defects are we talking about?

SUSAN DENTZER: The defects ranged all over the lot – cleft palates, club foot, these kind of structural defects, chromosomal defects like Downs Syndrome, congenital heart defects, really quite of a bit of a range. So they were serious defects. The interesting other crazy anomaly out of the study was that if you looked at minor birth defects, there were actually more kids born with minor birth defects who weren’t born through IVF and these assisted technologies, so not all of this hangs completely together.

GWEN IFILL: If one assumes that women who are more likely to use these techniques may be older or women or in order to take them – to use these techniques have to take a certain amount of drugs that they wouldn’t normally take, are those factors which also might result in these kind of defects? Is it that older women who are trying to use this are more susceptible?

SUSAN DENTZER: That is the $64,000 question that’s raised by these two studies. In the case of the major birth defects studies the researchers said there is no way to know whether this is due to the underlying condition of being infertile, the things that predispose a couple to seek infertility treatment, as you said, often are that they are of older age. It’s known that older women tend to have more infants born with Down’s Syndrome, for example. It’s not clear, the researchers said, whether it’s due to those factors or whether it’s due to the special factors, the kinds of interventions that you undergo through assisted reproductive technology — drug use that shuts down your hormonal system, then gears it up to produce multiple eggs, those kinds of things.

GWEN IFILL: Quickly, what should couples do with this information now?

SUSAN DENTZER: Most fertility experts say weigh the risks and be very acutely conscious now that we do have a very good study. It’s important to note that these are the largest studies that have been done date, therefore they are the most statistically valid, weigh the risks and take them into account as you contemplate whether to undergo these procedures, but recognize that at the end of the line you may in fact get a healthy baby.

GWEN IFILL: Susan, thank you very much.

SUSAN DENTZER: Thanks, Gwen.