Does induction ever improve health outcomes for the mother, baby or both?
A 2009 systematic review of the research on inductionMozurkewich, E., Chilimigras, J., Koepke, E., Keeton, K., & King, V.J. (2009). Indications for induction of labour: A best-evidence review. BJOG, 116(5), 626-636. found only two conditions for which induction seems to improve health outcomes. A later study answered an open question in this systematic review and identified a third situation in which induction can improve health outcomes.Koopmans, C.M., Bijlenga, D., Groen, H., et al. (2009). Induction of labour versus expectant monitoring for gestational hypertension or mild pre-eclampsia after 36 weeks' gestation (HYPITAT): A multicentre, open-label randomised controlled trial. Lancet, 374(9694), 979-988.In all three cases, differences in health outcomes were small and the studies left some important questions unanswered. Here are the three situations:
- Pregnancy lasting beyond 41 weeks: Various studies have compared induction of labor at or after 41 weeks with "watchful waiting" that involves repeated tests of fetal wellbeing between 41 and 42 weeks. Taken together, the studies suggest that for every 369 women who had labor induced between 41 and 42 weeks, one stillbirth or neonatal death may be prevented. The risk of meconium aspiration syndrome (an illness that causes serious breathing problems in the baby) may also be slightly lower. Induction between 41 and 42 weeks does not seem to increase the risk of C-section, and some studies have shown that it reduces this risk.
- Pre-labor rupture of membranes (PROM) at term (37-42 weeks): This is when membranes break on their own from 37 weeks onward, and labor hasn’t begun. A large randomized controlled trial compared immediately trying to induce labor with waiting up to three days for labor to begin and only inducing sooner if a complication developed. The study found that inducing right away was associated with a lower chance that the mother would develop an infection or the baby would go to the NICU. Immediate induction did not affect the likelihood of C-section, newborn infection or other important outcomes. However, most women in the watchful waiting group had vaginal exams before labor began, and those who carried Group B Strep (a bacterium that may be present in a woman's vagina and raises the risk of infection for the baby) were not given antibiotics to prevent infection. Many caregivers and researchers believe that avoiding vaginal exams until labor started and providing antibiotics to women with Group B Strep might have prevented the infections reported in the trial. These are standard practice in U.S. maternity care settings today.
- Increased blood pressure near the end of pregnancy: High blood pressure that develops in pregnancy may occur without other symptoms or signs (gestational hypertension) or with protein in the urine (preeclampsia, a more dangerous condition). High blood pressure can affect the flow of oxygen to the baby, increase the chance of complications during labor and lead to rare but very serious outcomes like stroke and seizures.
Researchers studied outcomes of women at or beyond 36 weeks of pregnancy who had gestational hypertension (diastolic blood pressure, the second number in a blood pressure reading, between 95 and 110) or mild preeclampsia (diastolic blood pressure between 90 and 110 and protein in the urine). The study found that inducing labor right away improved maternal outcomes. However, they defined "poor maternal outcome" to include any cases where women developed severe high blood pressure. Very few of these women experienced serious health problems as a result of the blood pressure increase. There were no significant differences in the number of serious problems like seizure, need for intensive care or postpartum hemorrhage, although the study was too small to show whether there were differences in these uncommon outcomes. There were also no significant differences in newborn outcomes, although a later study showed that neonatal intensive care admission, need for artificial ventilation (a machine to help the baby breathe), low birth-weight, and jaundice were more common the earlier a woman with mild gestational hypertension was induced, with best outcomes in the group induced after 38 weeks.Koopmans, C.M., Bijlenga, D., Groen, H., et al. (2009). Induction of labour versus expectant monitoring for gestational hypertension or mild pre-eclampsia after 36 weeks' gestation (HYPITAT): A multicentre, open-label randomised controlled trial. Lancet, 374(9694), 979-988; Barton, J.R., Barton, L.A., Istwan, N.B., et al. (2011). Elective delivery at 34(0/7) to 36(6/7) weeks' gestation and its impact on neonatal outcomes in women with stable mild gestational hypertension. American Journal of Obstetrics & Gynecology, 204(1), 44.e1-44.e5.
In the randomized controlled trial, women with mild preeclampsia (versus the more mild gestational hypertension), women having their first baby, and those with the least amount of cervical dilation were the most likely to benefit from early induction. This is most likely because preeclampsia is a more serious condition than gestational hypertension and first-time mothers and those who haven't begun dilating would have remained pregnant longer, providing more opportunity for their condition to worsen.