The Timing of Planned Delivery: Is It Time to Make the Case for 41 Weeks?

It has been almost 5 years since I coauthored a commentary on the timing of planned delivery in which I argued that data on improved outcomes continued to strengthen the case for delivery at 39 weeks’ gestation.^1,2  At the time, 37 weeks was considered term, and waiting until 39 weeks for planned deliveries had been gaining momentum on the basis of improved outcome data, quality improvement initiatives, and advocacy efforts.^3–5  Previously, “term” was an umbrella that encompassed anywhere from 3 weeks before to 2 weeks after the estimated due date. But given the difference in neonatal outcomes, especially in respiratory morbidity, the American College of Obstetricians and Gynecologists added further classifications and defined 37 + 0/7 to 38 + 6/7 weeks’ gestation as early term, 39 + 0/7 to 40 + 6/7 weeks’ gestation as full term, 41 + 0/7 to 41 + 6/7 weeks’ gestation as late term, and 42 + 0/7 weeks’ gestation and beyond as postterm.⁶  Today, most obstetricians follow guidelines and rather than act at 37 weeks, they wait until 39 weeks to induce low-risk nulliparous women.^7,8  But is it possible that 39 weeks is still too early? In this issue of Pediatrics, Hedges et al⁹  ask us to consider the timing of delivery once again.

The ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management) helped strengthen the case for induction at 39 weeks by showing a significant decrease in gestational hypertension, preeclampsia, rate of cesarean delivery, and neonatal respiratory support within the first 72 hours of life, as well as no statistical difference in perinatal mortality and severe perinatal morbidity, in low-risk nulliparous women.^5,7,10  Critique of the ARRIVE trial includes selection bias that threatens its external validity, calling into question the generalizability of its findings to all women.¹¹  Although each patient and provider must individually weigh the risks and benefits of induction between 39 and 41 weeks, the guidelines from the American College of Obstetricians and Gynecologists recommend not going past 42 weeks because of an increase in fetal mortality after 41 weeks when compared with 40 weeks.^12–14 

In this issue of Pediatrics, Hedges et al⁹  examine school performance by gestational age at birth, from 37 to 41 weeks, via teacher-reported math, science, and language skills at 9 years of age. In this US-based study, the authors report a positive association between gestational age and teacher-reported outcomes at 9 years old. Using a continuous measure of gestational age, the authors show a positive association with mathematics when children were delivered late term at 41 weeks and a negative association with language and literacy in children born at 37 to 38 weeks compared with term infants born at 39 to 40 weeks.⁹ 

These are significant findings and should not be taken lightly. This important research asks us to examine the balance between short- and long-term outcomes. We must admit, as obstetricians, we are often focused on immediate outcomes in the delivery room and the first few days of life. Is the infant breathing? Is the mother stable? But this study reminds us to think about the long-term outcomes, including not only physical health but social and emotional health as well as school performance. Those of us involved in maternal child health must continue to ask ourselves an important question: what defines an optimal outcome? It involves both mother and infant, short- and long-term, and it will take all of us working together, across the bassinette, to continue to do research and think broadly about achieving the best outcomes for all birthing people and their children.

This brings us back to the initiation of labor, which remains elusive. As clinicians, we continue to look for an answer to this difficult question: when is the optimal time to be born? For the mother? For the infant? And how do we measure outcomes? At birth? At 6 months? At 9 years? At 18 years? There may not be simple answers, but Hedges et al⁹  provide valuable data suggesting that improved school-aged performance is observed through 41 weeks.

The findings by Hedges et al⁹  are consistent with previous studies from the United Kingdom,^15,16  Scotland,¹⁷  New Zealand,¹⁸  Australia,¹⁹  Denmark,²⁰  Sweden,²¹  and the United States,^22,23  in which early term births are associated with poorer educational outcomes in school-aged children. Furthermore, Hedges et al⁹  report in this study on data from the Fragile Families and Child Wellbeing Study, which includes a large number of Black, Hispanic, and low-income families in US cities.²⁴  This suggests that the path to reducing disparities and achieving health equity might be furthered by examining practices around induction of labor and the timing of planned delivery.

Obstetricians and pediatricians must manage the delicate balance between timing of planned delivery and gestational age when it comes to perinatal outcomes. Collectively, we need more data, and we need to keep reevaluating this question as clinicians. There are many medical indications for early delivery, and clinical judgment will always be needed to manage the optimal time for birth. But this research adds weight to waiting for delivery based on the educational benefits seen at up to 41 weeks.