Maternal and perinatal outcomes after implementation of a more active management in late- and postterm pregnancies in Sweden: A population-based cohort study
Authors: Källén Karin , Norman Mikael , Elvander Charlotte , Bergh Christina , Sengpiel Verena , Hagberg Henrik , Svanvik Teresia , Wennerholm Ulla-Britt 
Published: January 2025

Background

The risk of perinatal death and severe neonatal morbidity increases gradually after 41 weeks of pregnancy. We evaluated maternal and perinatal outcomes after a national shift from expectancy and induction at 42+0 weeks to a more active management of late-term pregnancies in Sweden offering induction from 41+0 weeks or an individual plan aiming at birth or active labour no later than 42+0 weeks.

Methods and findings

Women with a singleton pregnancy lasting 41+0 weeks or more with a fetus in cephalic presentation (N = 150,370) were included in a nationwide, register-based cohort study. Elective cesarean sections were excluded. Outcomes during period 1, January 2017 to December 2019 (before the shift) versus outcomes during period 2, January 2020 to October 1, 2023 (after the shift) were analysed. For comparison, outcomes of pregnancies lasting 39+0 to 40+6 weeks (N = 358,548) were also studied.

Primary outcomes were: First, peri/neonatal death (stillbirth or neonatal death before 28 days); second, composite adverse peri/neonatal outcome (peri/neonatal death, Apgar score <4 at 5 min, hypoxic ischemic encephalopathy grades 1–3, meconium aspiration syndrome, birth trauma, or admission to a neonatal intensive care unit (NICU) ≥4 days); third, composite adverse peri/neonatal outcome excluding admission to NICU; and fourth, emergency cesarean section. Secondary outcomes included the components of the primary composite outcomes. Relative risks (RRs) with 95% confidence intervals (CIs) for binary outcomes period 2 versus period 1 were computed using modified Poisson regression analyses with adjustments for maternal age, parity, body mass index (BMI), smoking, and educational level.

Induction rates among pregnancies lasting 41+0 weeks or more increased from 33.7% in period 1 to 52.4% in period 2. Mean (standard deviation) gestational age at birth decreased from 290.7 (2.9) days to 289.6 (2.3) days. Infants born during period 2 were at lower risk of peri/neonatal death compared to infants born during period 1; 0.9/1,000 versus 1.7/1,000 born infants (adjusted RR 0.52; 95% CI [0.38, 0.69]; p < 0.001), and they had a lower risk of having the composite adverse neonatal outcome, both including (50.5/1,000 versus 53.9/1,000, adjusted RR 0.92; 95% CI [0.88, 0.96]; p < 0.001) or excluding NICU admission (18.5/1,000 versus 22.5/1,000, adjusted RR 0.79; 95% CI [0.74, 0.85]; p < 0.001). The cesarean section rate increased from 10.5% in period 1 to 11.9% in period 2 (adjusted RR 1.07; 95% CI [1.04, 1.10]; p < 0.001). For births at 39 to 40 weeks the adjusted RR for peri/neonatal death was 0.86 (95% CI [0.72, 1.02]). One limitation of the study is that we had no data on to what extent monitoring of fetal health was performed.

Conclusions

A more active management of pregnancies lasting 41+0 weeks or more was associated with a decrease in peri/neonatal deaths, and a decrease in composite adverse peri/neonatal outcomes. Increased rate of emergency cesarean sections was observed. Women with pregnancies advancing towards 41 gestational weeks should be given balanced information on the benefits and risks of induction of labour at 41 weeks compared to expectant management until 42 weeks and be offered induction of labour at 41 weeks or active surveillance of pregnancies from 41 weeks in order to decrease peri/neonatal mortality.