Cross-sectional study of associations between prior spontaneous abortions and preterm delivery.

Abstract

To evaluate associations between a history of spontaneous abortion and preterm delivery during subsequent pregnancies. The present secondary analysis included cross-sectional survey data related to all deliveries at 103 hospitals in Tehran, Iran, between July 6 and 21, 2015. Trained midwives interviewed patients within 24hours of delivery. Adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to investigate associations between spontaneous abortion and preterm delivery. Data were included from 4991 deliveries. A history of spontaneous abortion (OR 1.50, 95% CI 1.21-1.87; P=0.001) and history of recurrent spontaneous abortion (OR 3.74, 95% CI 1.90-7.37; P=0.001) were associated with increased odds of preterm delivery in comparison with no such history. Similarly, one (OR 1.33, 95% CI 1.04-1.70; P=0.023), two (OR 1.78, 95% CI 1.15-2.74; P=0.009), or at least three prior spontaneous abortions (OR 4.10, 95% CI 2.08-8.08; P=0.001) were associated with increased odds of preterm delivery compared with none. Population attributable fractions of 9.49% (95% CI 3.36-15.12) and 2.00% (95% CI 0.57-3.56) were calculated for histories of spontaneous abortion and recurrent pregnancy loss, respectively. History of spontaneous abortion and history of recurrent pregnancy loss were associated with increased odds of preterm delivery. A greater number of spontaneous abortions corresponded to greater odds of preterm delivery.