MONDAY, Sept. 16, 2002 (HealthDayNews) -- Surprising new research shows that twins and triplets born to older women are just as healthy as those born to younger mothers.
The findings, reported in the September issue of Fertility and Sterility, contradict conventional thinking about the health risks to children born to women over 35.
After examining national records of more than 150,000 multi-child pregnancies, the researchers found older mothers actually have babies with as few or fewer birth complications as young moms do.
"The findings were a surprise even to ourselves," says Dr. Jun Zhang, a researcher with the National Institute of Child Health and Human Development.
In general, twins and triplets are three or four times more likely than single babies to be born early, have a low birth weight or to die before birth or soon after, Zhang says. Meanwhile, single babies born to older women are much more likely to experience birth complications than those born to young women.
However, the statistics have become skewed in recent years by the extensive use of reproductive drugs, donor eggs and other assisted reproductive technologies. In the mid-1980s, only a few hundred babies were born per year by such methods. By 1999, that number had jumped to more than 30,000, according to the American Society for Reproductive Medicine.
Because these reproductive aids are more often used by older women, they are much more likely to result in twins or triplets. Between 1980 and 1999, the number of twins born to mothers over 35 grew from 4,097 to 22,894, while the number of triplet births went from 74 to 2,265, Zhang reports.
"Multiple pregnancies has become a more and more important issue for obstetricians, and for women themselves," he says.
Zhang's data, collected between 1995 and 1997 by the National Center for Health Statistics, probably will reassure older mothers about the safety of pregnancy. However, understanding why twins and triplets born to older women are safer than had been thought is a complex issue.
"The paradoxical phenomenon is due to a combination of medical and socioeconomic factors," he says.
For example, older women who use assisted reproductive technology or drugs are usually monitored more closely than younger mothers who conceive naturally. They are also more likely to get counseling or prenatal tests than young women.
Another reason is that natural twins and triplets, who often come from a single egg splitting, generally share the same placenta or amniotic sac. This leads to greater risks of them sharing infections, defects or other complications. By contrast, twins and triplets born through assisted technologies usually come from different eggs.
In addition to the medical factors, older mothers are generally more affluent and educated than younger ones, and more careful about risky behaviors when approaching pregnancy.
"The women who tend to use these methods are generally very motivated about their health, in terms of not smoking or drinking and getting doctor's treatment from the beginning," says Carol Wheeler, a physician with the Reproductive Science Center in Providence, R.I.
The age of a mother is only one factor in the health of her baby, Wheeler points out.
Zhang admits his research leaves out critical information about the mothers of twins and triplets, since it focused mainly on the health of the babies. Because of limitations in the records, the researchers weren't able to evaluate all aspects of birth by older women.
While the findings help prove that assisted reproductive technology and fertility drugs are safer than had been thought, Zhang emphasizes that women shouldn't wait until they are 35 to have children.
"I don't want to over-stress these results," he says. "If a woman has a choice, there is no good medical reason to delay childbearing. Our findings by no means advocate for fertility treatment."
What To Do
For information about infertility, visit the American Society for Reproductive Medicine.
To read a report about the success rates of assisted reproductive technology, visit the Centers for Disease Control and Prevention.
