December 13, 2017
2 min read

Inducing labor at 40 weeks in older women reduces perinatal death

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Women aged 35 to 50 years who had labor induced at 40 weeks gestation had nearly two-thirds lower risk for perinatal death than those who underwent expectant management, according to findings recently published in PLoS Medicine.

“A recent randomized controlled trial has shown that among nulliparous women aged older than 35 years, elective induction of labor at 39 weeks of gestation had no significant effect on the rate of cesarean section and no adverse short-term effects on maternal or neonatal outcomes compared with expectant management, but the trial was underpowered to examine the effect of induction of labor on the risk of perinatal death,” Hannah E. Knight, BA, MSc, of the department of health services research and policy, London School of Hygiene and Tropical Medicine, and colleagues wrote. “Well-conducted observational studies have found that induction of labor at term is associated with decreased perinatal mortality in the general pregnant population; however, none has been sufficiently powered to examine the impact on this specific age group known to be at increased risk.”

Researchers used Poisson regression models to compare existing perinatal mortality statistics between labor induction at 39, 40, and 41 weeks of gestation and expectant management in 77,327 nulliparous women in the U.K. aged 35 to 50 years who had delivered a singleton infant. Among the women, 33.1% had labor induced.

Confounding variables included socioeconomic quintile based on the Index of Multiple Deprivation score, birthweight percentile, baby’s sex, birth year, race and maternal age. Adjustments were made for pregnancy-related conditions such as fluid abnormalities, gestational diabetes, edema, preeclampsia, and pregnancy-induced hypertension when these were determined to have “significant coefficients.”

Knight and colleagues found that when compared with expectant management, inducing labor at 40 weeks was associated with a lower risk for in-hospital perinatal death (0.08% vs. 0.26%; adjusted RR = 0.33; 95% CI, 0.13-0.8) and meconium aspiration syndrome (0.44% vs. 0.86%; aRR = 0.52; 95% CI, 0.35-0.78) and a slightly increased risk for emergency cesarean section (aRR = 1.05; 95% CI 1.01-1.09) and instrumental vaginal delivery (aRR = 1.06; 95% CI, 1.01-1.11). A number needed to treat analysis indicated that 562 (95% CI, 366-1,210) labor inductions at 40 weeks would be required to prevent one perinatal death.

Current U.K. national guidelines recommend pregnant women be offered labor induction between 41 and 42 weeks of gestation to circumvent risks linked to long-term pregnancy, researchers noted.

“The number of first-time mothers over the age of 35 is rising. Although their risk of experiencing a stillbirth or neonatal death is relatively small, it’s still very important that these women receive the best advice on how to minimize the risks to themselves and their baby,” Knight said in a press release. “This study represents the strongest evidence yet that moving the offer of induction forward to 40 weeks might reduce the risk of stillbirth in this specific age group, which we know face a greater risk of stillbirth and neonatal death.”

She acknowledged that labor induction may not be acceptable to women and would also create an increased demand on health resources. – by Janel Miller

Disclosure: Healio Family Medicine was unable to determine authors’ relevant financial disclosures prior to publication.