THURSDAY, Oct. 30, 2003 (HealthDayNews) -- While increasingly sophisticated techniques for treating infertility now bring hope to couples, Danish researchers caution that infertile women who do eventually conceive may face a higher risk of birthing problems.
Researchers at the University of Aarhus, in conjunction with colleagues at the U.S. National Institutes of Health, found in a study of Danish births that women who had tried to conceive for more than one year -- a generally accepted definition of infertility -- were at greater risk for premature birth, low birth weight or Caesarean section.
Between 10 percent and 20 percent of women report their time to conception over one year long, the study says, and it was not only those women who had undergone fertility treatment that were at risk, but also those who eventually conceived naturally.
"The raw data showed high risks -- approximately 30 percent to over twice the risk," says lead researcher Olga Basso, a research associate professor at the University of Aarhus Epidemiology Science Center. "But when we adjusted the figures to account for such factors as age and obesity and smoking, the increase we saw was lower, but a still statistically significant association."
Basso says premature births were of particular concern.
"Increased risk of preterm births [before 37 weeks] is quite concerning," she says, "with estimated higher risks of almost 40 percent for first-time mothers and nearly 80 percent" for those with two or more children.
Her team analyzed nearly 56,000 births from the Danish National Birth Cohort study, where women were asked to report the length of time they took to conceive. The researchers found that among these women, about 11 percent had tried to conceive for more than a year; 15 percent were first-time mothers and 8 percent had already given birth.
"I think women should be concerned, but alarmed is too strong a term," says Christopher Ford, a senior research fellow in reproductive medicine at the University of Bristol. "The biggest risk, it seems, is a mild increase in prematurity between 34 and 37 weeks; that is not an enormous problem. If they were at higher risk for being born before 34 weeks, it would present a real problem, but I don't see that here."
"The risk of adverse birth is a relatively small risk and something you have to bear in mind, but not catastrophic," Ford adds. "It can sound quite bad that there is a 50 percent change in the odds, but that is different than change in the risk, and that's important."
Researchers say the study, one of the largest ever done on infertility and birth outcomes, shows doctors should be especially alert to potential problems that confront this group of women.
"I think that there are some things you maybe shouldn't do, like flying after your 30th week, or maybe reconsidering if you were going to have a home birth," Basso says. "But I really cannot give any advice on this, since that should be between the woman and her doctor to decide."
The results of the study appear in the November issue of Human Reproduction.
Complicating matters is a study, published earlier this year in the British Medical Journal, finding that women who had their babies too close together -- conceiving within six months after delivering -- faced similar risks.
More information
Learn about infertility from the American Society of Reproductive Medicine or the National Infertility Association. Learn about pregnancy from Childbirth.org.
