Importance: Fetal death during labor at term is a complication that is rarely studied in high-income countries. There is a need for large population-based studies to examine the rate of term intrapartum stillbirth in high-income countries and the factors associated with its occurrence.
Objective: To evaluate trends in term intrapartum stillbirth over time and to investigate the association between the trends and term intrapartum stillbirth risk factors from 1999 to 2018 in Norway.
Design, setting, and participants: This cohort study used data from the Medical Birth Registry of Norway from 1999 to 2018 to examine rates of term intrapartum stillbirth and risk factors associated with this event. A population of 1 021 268 term singleton pregnancies without congenital anomalies or antepartum stillbirths was included in analyses, which were performed from September 2022 to February 2023.
Exposure: The main exposure variable was time, which was divided into four 5-year periods: 1999 to 2003, 2004 to 2008, 2009 to 2013, and 2014 to 2018.
Main outcomes and measures: The primary study outcome was term intrapartum stillbirth. Risk ratios were calculated, and multivariable logistic regression analyses were conducted to identify factors associated with secular trends of term intrapartum stillbirth.
Results: The study population consisted of 1 021 268 term singleton births (maternal mean [SD] age, 29.72 [5.01] years; mean [SD] gestational age, 39.69 [1.27] weeks). During the study period, there were 95 term intrapartum stillbirths (0.09 per 1000 births). Maternal age, the proportion of individuals born in a country other than Norway, and the prevalence of gestational diabetes, labor induction, operative vaginal delivery, and previous cesarean delivery increased over the course of the study period. Conversely, the prevalence of infants large for gestational age, hypertensive disorder in pregnancy, and spontaneous vaginal delivery and the proportion of individuals who smoked decreased. The term intrapartum stillbirth rate decreased by 87% (95% CI, 68%-95%) from 0.15 per 1000 births in 1999 to 2008 to 0.02 per 1000 births in 2014 to 2018. Three in 4 term intrapartum stillbirths (70 of 95) occurred during intrapartum operative deliveries. The increased prevalence of older maternal age and obstetric risk factors were not associated with the variation in intrapartum stillbirth rates among the time periods. The prevalence of term intrapartum stillbirth was higher for individuals who gave birth in maternity units with fewer than 3000 annual births (adjusted odds ratio, 1.67; 95% CI, 1.07-2.61) than for those who gave birth in units with 3000 or more annual births.
Conclusions and relevance: Findings of this study suggest that, despite increases in maternal and obstetric risk factors, term intrapartum stillbirth rates substantially decreased during the study period. Reasons for this decrease may be due to improvements in intrapartum care.