Birth defects: When a 37 percent jump doesn't matter
Children conceived by means of some assisted reproductive technologies run a higher risk of being born with birth defects than do children conceived spontaneously, according to a new study in the journal Fertility and Sterility.
This has provoked some hand-wringing by University of Pennsylvania bioethicist Arthur Caplan, who observes that the study showed a "large increase" in the risk of having a child with a birth defect compared to the risk of defects in children made "the old-fashioned way"– a 37 percent increase.
"That is a huge number," Caplan asserts. "The large risk factor now on the table needs to be a key part of how everyone thinks about making babies in medical settings."
The researchers looked at the rate of birth defects reported in 46 studies of children born using regular in vitro fertilization (IVF), i.e. producing embryos by exposing eggs in a lab dish to sperm and then transferring them to a womb, as well as intracytoplasmic sperm injection (ICSI), in which a single sperm is injected directly into an egg. The studies, which encompassed the births of just under 125,000 children worldwide, also attempted to determine whether there was any difference in the birth defect rates between regular IVF and ICSI. They did not find much difference in the rate of birth defects between the two techniques.
Prior studies have also found an increase in birth defects among children born by means of assisted reproduction. So what is the magnitude of the risks? I am a bit puzzled about the way that Caplan characterized the results of the new study. What the researchers actually report is an increase in the relative risk of IVF and ICSI birth defects compared to the risk of birth defects among children born through what the fertility gurus label "spontaneous" conception. In the United States the rate of birth defects among children born by spontaneous means is about three out of 100.
What does a 37 percent increase in birth defects among IVF babies represent? Basically, it means that the researchers found that four out of 100 IVF babies are born with birth defects. That is not nothing, but it sure does sound less scary than a 37 percent increase.
How to account for this reported increase in birth defects associated with assisted reproduction? The researchers note that the defects could be due to the underlying infertility of couples seeking treatment. For example, one study found that children born to subfertile couples (often defined as those who took longer than one year to conceive) have a higher rate of birth defects. It is also possible that the laboratory handling of eggs and sperm and embryos somehow damages them and thus increases the risk of birth defects. However, one study that looked at a group of IVF kids with birth defects could not find evidence that the IVF lab procedures were the cause. And it may be that closer scrutiny of children born by means of all assisted reproduction results in a higher reported rate of birth defects, thus misleadingly boosting the apparent relative risk.
Based on this study, Caplan asserts, "We need to be sure that long-term monitoring of children born by means of infertility treatment is routine and that more research is done into the causes of health problems for kids who cannot make choices about facing risk."
First, as far as I can tell, most studies that have monitored IVF kids are reassuring. For example, a 2010 follow up study of IVF kids up to grade 12 reported, "IVF children scored higher on standardized tests than their matched peers, suggesting that IVF does not have a negative effect on cognitive development." (One earlier study had suggested that children conceived using IVF were taller than spontaneously conceived children, but a subsequent study found no such difference.)
Look, if these data stand up, then of course people who are considering using IVF should be told about the increased risks to their potential children. But how likely is it that parents would decide not to risk having a kid because there is a three percent chance they would suffer from a significant birth defect? That's the normal risk that any parent and any would-be kid face now. So raise the chance to four percent. How many people would change their minds about having a kid because of that increased risk? I suspect not too many.
Consequently, I am not quite sure what to make of Caplan's ominous assertion that seems to suggest that the risks faced by kids born via assisted reproduction are somehow more ethically significant than the risks faced by children born by conventional means.
Nobody gets to choose who their parents are or what their characteristics will be before birth. Assisted and spontaneously conceived kids stand in exactly the same ethical relation to their parents with regard to the risks of being born.
Downtown Charlottesville denizen Ronald Bailey is the science correspondent for nationally-circulated Reason magazine (where this essay first appeared) and the author of "Liberation Biology: A Moral and Scientific Defense of the Biotech Revolution."