Impact of 2 years of COVID-19 pandemic on preterm birth: Experience from a tertiary center of obstetrics in western Germany.

Objective: To compare preterm birth rates and reasons before and during the COVID-19-pandemic using a monocentric, retrospective study.

Methods: Univariate analysis identified differences in rates and reasons for preterm birth and neonatal outcomes between the pre-pandemic period (January 1, 2018 to December 31, 2019) and during the pandemic (January 1, 2020 to December 31, 2021) among all births at our tertiary obstetrical center, the University Hospital of Essen.

Results: The cohort consisted of 6086 deliveries with 593 liveborn preterm singletons. During the pandemic, the incidence of preterm birth decreased (10.7% vs. 8.6%; odds ratio [OR] 0.79; 95% confidence interval [CI] 0.66-0.93). Spontaneous preterm birth (43.2% vs. 52.3%; OR 1.47; 95% CI 1.05-2.03), and placenta accreta spectrum disorder (3.7% vs. 8.2%; OR 2.36; 95% CI 1.15-4.84) were more common reasons for preterm birth. Placental dysfunction was a less common reason (34.1% vs. 24.3%; OR 0.62; 95% CI 0.43-0.90). Incidences of preterm premature rupture of membranes (28.13% vs. 40.25%; OR 1.72; 95% CI 1.12-2.43) and oligo-/anhydramnios (3.98% vs. 7.88%; OR 2.06; 95% CI 1.02-4.21) increased. Iatrogenic preterm birth decreased (54.5% vs. 49.5%; OR 0.81; 95% CI 0.58-1.13). Stillbirth rates did not change significantly. Among term births, there were fewer spontaneous deliveries (71.0% vs. 65.8%; OR 0.78; 95% CI 0.69-0.88), and more elective (12.3% vs. 15.1%; OR 1.26; 95% CI 1.07-1.50) and unplanned (9.3% vs. 10.9%; OR 1.19; 95% CI 0.98-1.45) cesarean sections. During the pandemic, more term newborns were admitted to neonatal intensive care (1.4% vs. 2.5%; OR 1.86; 95% CI 1.20-2.88).

Conclusion: Our results, in line with data from other high-income countries, suggest that the likely reason for the decreased preterm birth rates is the underdiagnosis of pregnancy complications.