In Vitro Linked to Rare Bladder Defects
Disorder Among Conditions Linked to Babies Born Through In Vitro Fertilization
In vitro fertilization, retrieved eggs and sperm from the parents are placed together in a laboratory dish to enhance the likelihood of fertilization. If it occurs, the eggs are transferred back into the woman's uterus, where implantation and embryo development would hopefully occur as in a normal pregnancy.
There are various theories on why in vitro fertilization-conceived children seem to have a higher risk of medical problems -- from problems with the preserving solution in the dish that houses the sperm and egg to mistakes in the procedure itself. "Our theory is that bladder exstrosphy and other defects could result from mishandling of the fertilized egg during implantation or some kind of metabolic problem induced by the procedure of implantation itself," Gearhart tells WebMD.
But Robert Brzyski, MD, PhD, president of the professional association representing in vitro specialists at 370 clinics across the U.S., has his own theory. "We cannot discount the lab environment or other factors, but something in the couple's inability to naturally have a child may predispose them to adverse outcomes in general," says Brzyski, of the Society for Assisted Reproductive Technologies and an ob-gyn at the University of Texas Health Science Center at San Antonio.
Like other assisted reproductive techniques, in vitro fertilization is usually reserved for couples who cannot conceive a child naturally for at least a year.
Another theory under investigation is the fact that many in vitro fertilization conceptions end with multiple births, which are historically more vulnerable to birth defects. Of the 78% in vitro fertilization-assisted pregnancies that result in a live birth, 50% produce a single child, 24% produce twins and 5% are triplets or more, reports the American Society of Reproductive Medicine.
"Even before in vitro fertilization, there was a recognition that children that were the result of multiple birth had a higher risk of birth defects," Brzyski tells WebMD. "So now that we have a technology that is associated with increased risk of multiple births, it's hard to know if it's the technology itself or the natural expression of some process involved in multiple births that may be causing these defects. But when you talk about an extremely rare condition, even with a seven-fold increase, that condition is still extremely rare."
Some 45,000 American children have been born through in vitro fertilization since the first procedure was done in the U.S. in 1981; worldwide, more than 1 million babies followed the 1978 birth of the first so-called "test tube baby," Louise Brown.
"The vast majority of in vitro fertilization babies are healthy, robust, and wonderful infants," says Gearhart. "At the end of day, in vitro pregnancy has been a wonder for couples who have waited years to have a baby."