Lab-Conceived Babies at Higher Risk of Defects

WEDNESDAY, March 6, 2002 (HealthDayNews) -- Babies conceived through assisted reproductive technology (ART) are twice as likely to suffer major birth defects as infants conceived the natural way, according to a new study.

The odds of having a baby with at least one major birth defect are still quite low -- about four in 100 for a natural conception and eight to nine in 100 for babies born through assisted reproduction. But the findings, appearing in tomorrow's New England Journal of Medicine, are the latest to show that while fertility clinics may be the last resort for childless couples, their services are far from risk-free.

A second report in the journal finds an additional problem with the procedure: The babies tend to weigh less. Although this is often the result of multiple births, a common by-product of assisted reproduction, the report says even a single newborn is likelier to have a lower birth weight.

The evidence that assisted reproduction isn't merely as simple as giving nature a helping hand has been mounting steadily. Earlier this winter, for example, Swedish scientists reported that babies born through assisted reproductive techniques are roughly three times as likely as naturally conceived children to develop cerebral palsy. The risk of the disorder is even greater for twins, triplets and other multiple-order pregnancies.

For the newest findings, researchers in Australia and the United Kingdom performed a similar review, looking for major birth defects in babies born in western Australia between 1993 and 1997.

Of those, 301 were conceived through a procedure called intracytoplasmic sperm injection (ICSI), in which doctors plant individual sperm into eggs. Another 837 were born as a result of other in vitro, or test dish, techniques, and 4,000 were conceived the old-fashioned way.

By their first birthday, 26 (or 8.6 percent) of the ICSI babies had been diagnosed with a major birth defect, such as heart, muscle or gastrointestinal problems or chromosomal abnormalities. That figure was 9 percent for the in vitro babies, but only 4.2 percent for the naturally conceived children.

After adjusting the analysis for the mother's age, the number of children she had, and other factors, the researchers found that the risk of birth defects was twice as high for babies conceived in the lab.

Dr. Jennifer Kurinczuk, a reproductive endocrinologist at the University of Leicester in England and a co-author of the study, said the results are likely to be controversial. "I guess that there will be quite a lot of debate about what our findings mean," she said.

However, Kurinczuk defended the study as "robust." She added, "These procedures are not risk-free procedures, and people shouldn't be complacent about them."

The researchers didn't compare rates of cerebral palsy in the three groups, because the defect can't be accurately diagnosed until children are about 5 years old. Kurinczuk said they plan to conduct that study when they can.

In the second study, researchers at the U.S. Centers for Disease Control and Prevention found that assisted reproductive technologies increase the risk that babies will be born lightweight.

U.S. infants conceived through ART made up 0.6 percent of all babies born to mothers at least 20 years old in 1997, but they accounted for 3.5 percent of all low-birth weight and 4.3 percent of very low-birth weight infants born then. Low birth weight is considered to be about 5.5 pounds, while very low birth weight is about 3.3 pounds or less.

What's surprising about that study, the scientists said, is that the risk applied to singletons, even when adjusted for length of gestation. But while ART was associated with greater odds of multiple births, it didn't seem to worsen their already lower chances of being normal weight.

Some evidence suggests that ART procedures may produce hormonal and placental abnormalities that restrict the growth of the developing fetus.

Pamela Madsen, executive director of the American Infertility Association, a New York City-based advocacy group, called the studies "important," but said they weren't reason enough to discourage parents from seeking assisted reproductive technologies.

"I think that patients have to be informed that if you are infertile and you have reproductive disease issues, that you may be at a higher risk for a more difficult pregnancy and you may have a higher risk for a very small percentage of birth defects," Madsen said. "Patients that may have a high-risk pregnancy need to take better care of themselves."

Some of the birth defects in the Australian study involved the urinary and reproductive tracts. Madsen noted that those problems, such as undescended testicles, have previously been associated with ICSI and may simply reflect reproductive hurdles inherited from an infertile -- but not sterile -- father.

"Would that prevent you from having a child, if the child inherited the father's difficulty with fertility, when these men are living happy lives? I would think that most infertile couples would gladly" go ahead with the procedure, she said.

More than 28,000 babies were born in the United States in 1998 through ART, according to the CDC.

What To Do

The Centers for Disease Control and Prevention has issued a report on the impact of assisted reproductive technologies.

For more on fertility treatments, try the American Society for Reproductive Medicine or the American Infertility Association.