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Babys Weight In Vitro*

March 7, 2002


In Vitro Babies Have Bigger Risks

Of Health Problems, Studies Say



Women who become pregnant using in vitro fertilization and other assisted reproduction methods face twice the risk of bearing infants with low birth weight or birth defects compared with those who conceive their children naturally, researchers have found.

Doctors had long warned that the procedures often result in multiple births, raising the risks of health problems for the newborns. But two new studies, published in Thursday's New England Journal of Medicine, suggest that the offspring of women bearing a single child also face heightened health risks.

Both studies' authors caution that they didn't address the reasons behind the increased health risks. The underlying medical causes of the couple's infertility, rather than the drugs and procedures themselves, could be responsible for birth defects and low birth weights, they say.

Some fertility specialists and patient advocates criticized the studies' methods and conclusions, saying they would raise unnecessary fears for infertile couples facing the ordeal of using medical technology to have children.

But in an editorial accompanying the articles, Allen A. Mitchell, a professor of epidemiology at Boston University School of Public Health, said the research raises questions about the aggressive marketing of costly infertility treatments, which he says could be leading some couples to seek intervention earlier than necessary.

For these patients, the treatments "may not be a risk they want to take," Dr. Mitchell said in an interview. Still, he said, the vast majority of couples who use assisted reproduction methods will be unaffected by these problems. The likelihood of having a single child, born to term, of normal birth weight using reproductive technology is 94%, and having a child free from major defects is 91%, according to the studies.

About 10% of U.S. couples trying to have a child face problems with infertility, defined as the failure to conceive a child after 12 months of intercourse without contraception.

In one study, researchers at the U.S. Centers for Disease Control and Prevention in Atlanta examined government-required records of 42,463 U.S. babies born in 1996 and 1997 and conceived with assisted reproduction technology, including in vitro fertilization, in which egg and sperm are joined in a petri dish and then introduced into the uterus.

Among parents who used assisted reproduction technology to bear a single child to term, 6.5% of those children were born with low birth weights -- 2.6 times the rate researchers would have expected in the general population. Infants with low birth weights -- less than 5 pounds, 8 ounces -- are at higher risk for infections, developmental disabilities and death.

The second study examined a public registry of 1,138 children born from 1993 to 1997 at three private clinics in Western Australia. The children were conceived using two assisted reproduction techniques, in vitro fertilization and intracytoplasmic sperm injection, in which a single sperm is selected and injected into an egg as part of an IVF procedure.

Researchers found that about 9% of those infants were diagnosed with one or more major birth defects by age one, compared to 4.2% in a sample of 4,000 conceived naturally. The results were similar when multiple births were excluded and didn't appear to be explained by the age of the mother, researchers said. Among the defects: heart abnormalities and children born with one kidney instead of two.

Based on these findings, patients "shouldn't assume these procedures are risk-free," said Jennifer J. Kurinczuk, an author of the study, now a senior lecturer at the University of Leicester in England.

But some infertility specialists said earlier studies contradicted the study on birth defects. Zev Rosenwaks, director of the center for reproductive medicine and infertility at the Weill Medical College of Cornell University in New York, called the studies "far from convincing" and said infertility patients often are examined and tracked more carefully than patients in the general population, skewing results.

But the authors of the New England Journal of Medicine studies said differing levels of scrutiny among patients and other possible methodological problems didn't appear to explain the results.

Write to John Hechinger at john.hechinger@wsj.com1

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