Fertility treatments balance risk and reward

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.