Interpregnancy interval following missed abortion and the risk for preterm birth

Short inter-pregnancy interval (IPI) of <18 months following a live birth, has been associated with adverse pregnancy outcome. This study aimed to evaluate whether a short IPI following a medically treated missed abortion (MA) poses similar perinatal risks in a subsequent pregnancy.

The retrospective analysis included patients with history of an MA at up to 10 weeks of gestation, treated with misoprostol (pgE1) only, and with a documented subsequent live pregnancy (2010-2022). 1110 Patients were allocated into two groups: IPI ≤18 months and IPI >18 months. The primary outcome was the risk for a spontaneous preterm birth (PTB) <37 weeks of gestation in the consecutive pregnancy. Secondary outcomes included maternal and neonatal adverse outcomes. Statistical analysis was performed using the Statistical Program for Social Sciences for Windows version 26 (SPSS Inc, Chicago, IL).

The cohort included 1,110 patients: 430 (38.74 %) patients with IPI <18 months and 680 (61.26 %) patients with IPI >18 months. The characteristics of the two groups were not significantly different. The rates of spontaneous PTB <37 and <34 weeks of gestation were significantly higher in the short vs. long IPI cohort (16.28 % vs. 7.06 % and 6.74 % vs. 5.0 %, respectively, p < 0.05). These patients also had a higher risk for Cesarean delivery (31.63 % vs. 23.34 %, p = 0.005) and postpartum hemorrhage (4.42 % vs. 2.06 %, p = 0.029) compared to patients with IPI >18 months. The observed differences remained statistically significant even after adjusting for potential confounding variables using multiple regression analysis. No other significant differences in neonatal or maternal outcomes were noted.

Short IPI (≤18 months) following a medical treatment MA may be associated with an increased risk of PTB, Cesarean delivery and PPH.