To Wait or Not to Wait

Labor induction potentially a little safer than natural labor after 37th pregnancy week

(RxWiki News) Once a woman reaches full term in her pregnancy, it can be hard not to wish the baby would arrive already. Fortunately, choosing to be induced is no riskier than waiting for labor.

A recent study has found that women whose labor is induced at the 37th week of pregnancy or later have slightly better outcomes for the mother and child than women who wait for a natural start of labor.

"Induced labor for pregnancies at term is safe."

Lead author Sarah Stock, a lecturer in maternal fetal medicine at the University of Edinburgh's Queen's Medical Research Institute, and colleagues wanted to find out the rate of serious complications and deaths for babies born at term to mothers who were induced compared to mothers who waited for labor to start naturally.

The researchers looked at the data on over 1.27 million pregnancies in Scotland between 1981 and 2007 in which the baby was born after the 37th week.

They factored into their calculations the baby's birth weight, the precise week the baby was born and whether the mother had given birth before.

They also looked at whether the pregnancy resulted in a C section, whether the mother experienced a hemorrhage, any birth-related injuries to the mother and whether the baby was admitted to a special care unit.

For babies born between 37 and 41 weeks, those who were born following induced labor had lower death rates than those who were born to mothers waiting for labor to begin naturally.

For instance, among 40-week pregnancies, 37 of 44,764 babies died to mothers who were induced, which is an overall rate of 0.08 percent. Among the 350,643 women who waited for natural labor, 627 babies died, for a rate of 0.18 percent.

Although the rate of cesarean sections was not higher in the pregnancies with induced labor, this group did show an almost one percent increased rate of admissions to neonatal care units compared to the natural labor onset group. The C section group had 8 percent admissions and the natural onset group had 7.3 percent.

The researchers also found that hemorrhaging was less likely in women whose labor was induced if they were at their 38th week of pregnancy or later, compared to women whose labor began naturally.

They also determined that a woman with an induced labor at 39 or 40 weeks was less likely than those with natural-onset labor to have a tear or injury with her anal sphincter, the muscle that controls the anus.

Another way to think of this, explained the authors, is that one baby in every 1,040 might be saved from death if the mother is induced, but seven more would end up in the NICU.

The authors said that other factors that they did not measure could have played a part in the results they found but that overall, it appears that a lower rate of infant deaths might occur among women who choose to be induced once they are at term in their pregnancies.

The study was published online May 10 in the journal BMJ. The research was funded by the Chief Scientist Office of the Scottish Government Health Directorate. The authors declared no competing interests.

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Review Date: 
May 11, 2012