In vitro and birth defects

By SHERRY JACOBSON
KNIGHT RIDDER NEWSPAPERS
As Louise Brown nears her 25th birthday, no one can deny the success of in vitro fertilization in solving infertility problems for many people around the world.
Since her birth July 25, 1978, as the first so-called "test tube" baby, more than 200,000 infants have been born in the United States alone using vastly improved artificial reproductive technology.
But as the quarter-century mark approaches, a snapshot of in vitro fertilization does not always show happy families with gurgling babies. Some of the children have significant health problems that may result from how they were conceived. New research is focusing more attention on their higher incidence of birth defects.
A recent Australian study suggests that infants conceived by assisted reproductive technology, which includes in vitro and related procedures, have twice the risk of major birth defects as those conceived naturally. The defects include such problems as clubfoot, shortened limbs, heart malformations and anomalies of the sex organs.
The prevalence of such major defects was 4.5 percent in the natural-conception group and 9.4 percent in the in vitro fertilization group, noted the study, which was published in March in The New England Journal of Medicine. Minor birth defects that could be repaired by surgery, such as extra fingers and toes, also were more common among the in vitro babies.
Multiple births a factor?
Previous studies of in vitro infants had suggested that such defects could result from a higher-than-normal incidence of multiple births. Giving birth to twins, triplets or more babies at once greatly increases the likelihood of premature delivery and other complications. However, the latest study disputed that notion.
"The increase in the risk of a major birth defect associated with assisted conception remained significant when only [single births] were considered," wrote lead researcher Michele Hansen of the University of Western Australia in Perth.
The study identified 101 babies with birth defects among 1,138 infants born after in vitro fertilization, compared with 168 of the 4,000 naturally conceived babies.
Call for more research
Some researchers are calling for a better way of tracking the health of children conceived by in vitro methods. Most of the follow-up studies to date have included only small groups of children until age 1, by which time a majority of physical anomalies are considered to be detectable. But researchers wonder whether other developmental problems are being missed.
"It is imperative that detailed and careful follow-up is carried out on children born as a result of assisted reproductive technologies," wrote Robert M.L. Winston and Kate Hardy of The Wolfson and Weston Research Centre for Family Health at Imperial College in London. "Bringing a child into the world is a serious human responsibility. We cannot ignore the clouds lowering over these valuable therapies."
Their report was part of a special supplement, titled "Fertility," published this month by the scientific journals Nature Cell Biology and Nature Medicine. The supplement includes not only the latest research on contraception and fertilization but also a frank assessment of problems that plague reproductive technology.
Role of infertility
Previous reports raised other possible reasons for defects besides multiple births. Some fertility experts say more studies are needed on in vitro babies born with birth defects to consider whether the defects stem from medical conditions that caused a parent's infertility.
"We know that if you are infertile, you have a higher risk of having a baby with a birth defect," says Dr. Sandra Ann Carson, a Houston reproductive endocrinologist and president of the American Society for Reproductive Medicine. Studies also have shown that in vitro babies are more likely to be underweight and premature at birth, she notes.
Dr. Carson suggests doing "a better study" that would compare the rate of birth defects in babies born after in vitro treatment with the defects in babies born to infertile parents who used other fertility treatments such as hormones or surgery. "That would tell us if the defects were the result of the parents' infertility or the in vitro treatments," she says.