It's NOT something I'm entirely proud of, but I can't seem to stop myself from doing it. Each week, when my teenage daughter's copy of Us Weekly magazine arrives, I'm compelled to read it. Last week's cover story really grabbed my attention: "It Was in Vitro! The Untold Story Behind Angelina and Brad's Twins."
As the magazine tells it, Angelina Jolie and Brad Pitt's latest additions, Knox and Vivienne, were conceived through the use of assisted reproductive technology, specifically in vitro fertilization. The couple chose to go this route, the magazine's source said, not out of medical necessity but as a matter of convenience and expediency.
Whether the story is true, reproductive technology is not something to be entered into lightly. For starters, the procedures have their own drawbacks, ones that are not fully understood.
"There are several categories of risk associated with the use of ART," says Dr. Marcelle Cedars, director of reproductive endocrinology at UC San Francisco.
Those related directly to the pregnancy are probably most clear-cut. Pre-term labor and placental abnormalities (such as placental abruption, in which the placenta separates from the uterus) are increased roughly twofold among women who undergo assisted-reproductive procedures than those who get pregnant naturally, and children conceived using these technologies are about twice as likely to be born prematurely and to be underweight at birth.
The use of assisted-reproductive technology may create problems that extend beyond the pregnancy too. "It looks as though there's an increased risk of some congenital birth defects," Cedars says. Hypospadiasis, a condition in boys in which the opening of the urethra is on the underside of the penis, not at the tip, seems to be a particular problem. There may also be an increased risk of some gastrointestinal tract abnormalities.
And although the technology is often used to bypass male infertility problems caused by chromosomal abnormalities, it doesn't eliminate the underlying genetic problem, which a child then inherits. Preimplantation genetic diagnosis (or PGD) allows embryos to be screened for certain genetic diseases before they are implanted, but it is unable to detect all of these problems.
Other genetic problems might arise as a result of the process itself. Subtle genetic changes can occur while an embryo is developing in the laboratory, causing certain rare conditions and, some reproductive experts worry, contributing to a variety of childhood cancers.
But the greatest danger comes from implanting more than one embryo at a time, something often done to try to guarantee a successful outcome and eliminate the need to perform the procedures repeatedly. (Such procedures are costly, and failed attempts can be frustrating for couples going through the process.) "Across the board, the biggest risk of ART stems from the increased likelihood of multiple births," Cedars says. According to the Centers for Disease Control and Prevention, about 45% of pregnancies conceived with assisted reproductive technology result in twins and roughly 7% in triplets or more.
Carrying more than one baby dramatically increases the chances of pregnancy-related complications. More than half of twins and more than 90% of triplets are born prematurely, and women expecting multiple births are at extra high risk of developing conditions such as high blood pressure and diabetes.
To reduce the likelihood of multiple pregnancies, the Society of Assisted Reproductive Technology and the American Society for Reproductive Medicine have established guidelines for the number of fertilized embryos to be transferred to the uterus during a cycle of infertility treatment. For women younger than 35, they recommend transferring no more than two embryos at a time and suggest that one embryo may be sufficient for those women who are most likely to become pregnant.
Researchers are also studying new ways to identify the best embryos to transfer. "If we can determine which embryos are most likely to take, we can decrease the number that are transferred and reduce the risk of a multiple pregnancy," Cedars says.
Sometimes the hardest thing to do, however, is to convince patients that they don't want a multiple pregnancy. Men and women trying desperately to conceive often love the idea of having twins or even triplets. They get the family they want without the trouble (and expense) of going through infertility treatments all over again.
"While the goal is to help patients with family building, patients want a healthy baby," Cedars says. "We want to make sure we're not adding to the risk with ART." Additional research will help determine exactly how safe or risky these procedures are, identifying ways to improve them.
For couples struggling with infertility, these technologies may be the only option. They are not intended for those who simply grow impatient with trying to get pregnant the old-fashioned way.