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The impact of induction of labor at 39 weeks on the incidence of stillbirth in low-risk women

Published:March 17, 2020DOI:https://doi.org/10.1016/j.ajog.2020.03.009
      To the Editors:
      We read with interest the Research Letter by Po’ et al.
      • Po' G.
      • Oliver E.A.
      • Reddy U.M.
      • Silver R.M.
      • Berghella V.
      The impact of induction of labor at 39 weeks in low-risk women on the incidence of stillbirth.
      The study described the stillbirth rate per week in the United States from the 39th gestational week onward in low-risk women. The purpose was to determine the impact of induction of labor at 39 weeks on the stillbirth rate in low-risk women. The impetus for the study was based on the results of the ARRIVE trial.
      • Grobman W.A.
      • Rice M.M.
      • Reddy U.M.
      • et al.
      Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network
      Labor induction versus expectant management in low-risk nulliparous women.
      The ARRIVE trial, first published in August 2018, was designed to determine whether induction of labor at 39 weeks gestation of low-risk nulliparous women reduces the risk of a composite outcome of perinatal death or severe neonatal complications (the primary outcome) as compared with expectant management.
      • Grobman W.A.
      • Rice M.M.
      • Reddy U.M.
      • et al.
      Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network
      Labor induction versus expectant management in low-risk nulliparous women.
      The authors determined that labor induction did not quite significantly decrease the primary outcome (4.3% in the induction group vs 5.4% in the expectant management group; relative risk, 0.80; 95% confidence interval, 0.64–1.00; P=.049, statistical significance adjustment to <.046) and therefore concluded that a policy of induction of low-risk nulliparous women at 39 weeks was reasonable.
      Po’ et al
      • Po' G.
      • Oliver E.A.
      • Reddy U.M.
      • Silver R.M.
      • Berghella V.
      The impact of induction of labor at 39 weeks in low-risk women on the incidence of stillbirth.
      assume that the same conclusions are valid for all low-risk women, not only nulliparous women. The stillbirth data presented as differentiated from the prospective stillbirth rate proposed by Po’ et al is shown in the Figure. In other words, the “background” risk of stillbirth remains unchanged up to the end of 41 weeks gestation. Similar results would be expected if the variable was hypertension, eclampsia, oligohydramnios, meconium aspiration, placental abruption, shoulder dystocia, among others.
      Figure thumbnail gr1
      FigureStillbirth rates per gestation week
      Data from Po’ et al.
      • Po' G.
      • Oliver E.A.
      • Reddy U.M.
      • Silver R.M.
      • Berghella V.
      The impact of induction of labor at 39 weeks in low-risk women on the incidence of stillbirth.
      Peleg. Letter to the editor. Am J Obstet Gynecol 2020.
      We believe it is unjustified to extrapolate the results of the ARRIVE trial to all low-risk women. Before induction of labor at 39 weeks gestation becomes routine, we suggest that more research be published with transparency of data. Until that time, we remain disinclined to offer induction of labor as standard of care at 39 weeks to low-risk women, nulliparous or parous.

      References

        • Po' G.
        • Oliver E.A.
        • Reddy U.M.
        • Silver R.M.
        • Berghella V.
        The impact of induction of labor at 39 weeks in low-risk women on the incidence of stillbirth.
        Am J Obstet Gynecol. 2020; 222: 88-90
        • Grobman W.A.
        • Rice M.M.
        • Reddy U.M.
        • et al.
        • Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network
        Labor induction versus expectant management in low-risk nulliparous women.
        N Engl J Med. 2018; 379: 513-523

      Linked Article

      • The impact of induction of labor at 39 weeks in low-risk women on the incidence of stillbirth
        American Journal of Obstetrics & GynecologyVol. 222Issue 1
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          A large randomized trial showed that induction of labor between 39 0/7 weeks and 39 4/7 weeks in nulliparous low-risk women without medical indications for induction was associated with a trend for less perinatal morbidity and mortality, significantly fewer cesarean deliveries, and fewer hypertensive disorders compared to expectant management.1 The objective of this study was to evaluate the impact of induction of labor between 39 0/7 weeks and 39 4/7 weeks on the incidence of stillbirth in low-risk women in the United States.
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        American Journal of Obstetrics & GynecologyVol. 223Issue 1
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          We thank Drs Peleg and Warsof for their letter regarding our manuscript entitled “The impact of induction of labor at 39 weeks in low-risk women on the incidence of stillbirth.” We acknowledge that the background risk of stillbirth increases after 41 weeks gestation. This is applicable to women regardless of their parity.
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