NEW YORK, Mar 28 (Reuters Health) - Nearly twice as many women had their labors induced in the late 1990s compared with a decade earlier, according to an analysis of medical records.

The findings are based on the hospital records of nearly 1,300 women with induced term deliveries and their babies, over a 16-year period. All women gave birth at a health center in Rochester, Minnesota.

"Physicians and midwives need to carefully and honestly evaluate the risks and benefits of the increased use of induction of labor that are accruing to pregnant women and their infants," Dr. Barbara P. Yawn and colleagues from the Mayo Clinic and Olmsted Medical Center in Rochester, conclude. The study is published in the March issue of the American Journal of Obstetrics and Gynecology.

Nearly 26% of pregnancies that went to term (37 weeks) were induced in 1995, compared with about 13% in 1980, the investigators found. While inducing labor with drugs is necessary in some cases, it carries risks to both the mother and fetus.

The study found a 23-fold increase in the rate of induction for macrosomia, or an abnormally large fetus, and a 15-fold increase in the rate of women who opted to be induced for unspecified reasons.

Higher rates of cesarean delivery were noted among women who were induced for macrosomia. Cesarean deliveries have more complications, a longer recovery time, and are more expensive.

Twice as many pregnancies were induced in 1995 than in 1980 because they lasted beyond the date at which the pregnancy was expected to occur, the researchers found. And the average gestational age at which a pregnancy was induced declined to 41.0 weeks from 41.9 weeks.

The rate of cesarean delivery rose to 18% in 1987 from 5% in 1980, and the number of days a woman remained hospitalized after delivering also increased.

However, the number of pregnancies induced because of premature rupture of membranes declined to 0.2% from 4.3%. Premature rupture of membranes refers to a break of the amniotic sac that protects the fetus during pregnancy.

Previous studies have demonstrated the medical benefits of inducing labor to avoid premature rupture of membranes, but not for inducing labor for an abnormally large fetus. The research has been mixed over whether there is any medical benefit associated with inducing labor before 42 weeks gestation. Most babies are born around 40 weeks gestation.

The authors conclude that the increase in induced labor for elective reasons has resulted in longer maternal hospital stays and more cesarean deliveries.

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