SAN DIEGO—When Louise Brown was born on 25 July 1978, she kicked off an era. The first "test tube baby" is a mother herself now, and she's been joined by millions of others born with the help of in vitro fertilization (IVF). At a press conference this morning at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW), infertility specialists talked about whether people who were conceived by IVF are likely to be healthy.
"By and large, the kids are just fine. It's not like the kids have extra arms or extra heads or anything," says Carmen Sapienza, a geneticist at Temple University in Philadelphia, Pennsylvania. But none is older than their early 30s, and the vast majority are under the age of 20, so they haven't had time for long-term health problems to show up.
One source of worry is that so many IVF babies have low birth weight. Children conceived through IVF are more likely to weigh less than 2.5 kilograms than are babies conceived naturally. That's not just because so many IVF babies are twins or other multiple births; the same is true for single babies. That could spell trouble ahead, because low-birth-weight babies often have long-term health problems. They're more likely to be obese, to have diabetes, and to have hypertension when they're 50, for example.
With that in mind, Sapienza and colleagues have looked at genes that are likely to play a role in such health problems. They’ve examined genes involved in insulin and glucose metabolism, for example, to see whether there's a difference in how those genes are expressed in children born from IVF and children who were conceived naturally.
The upshot? For 5% to 10% of those genes, the DNA methylation patterns, which affect how genes are expressed, are different between IVF and non-IVF children. There's no way to tell if that's because of the technology used to produce the IVF babies or whether the difference has something to do with the underlying infertility problem the parents had. It’s also unclear whether these gene-expression differences will translate into health differences. But it does suggest that children conceived by IVF are unique on some level.
"From my perspective, more data is better," says Sapienza. "People get upset" about data that sounds like an attack on IVF. But if it turns out that children who were conceived by IVF had a higher risk of, say, colon cancer, he says, it would be useful to be able to tell them to get screened earlier.