The duration of gestation at previous induced abortion and its impacts on subsequent births: A nationwide registry-based study.

INTRODUCTION

Previous induced abortions have been associated with adverse birth outcomes. However, only a few studies have considered the possible influence of gestational age at induced abortion. Therefore, this study aimed to identify the impacts of gestational age during prior induced abortion(s) on subsequent births among first-time mothers in Finland.

MATERIAL AND METHODS

First-time mothers (n = 418 690) with singleton births between 1996 and 2013 were identified from the Finnish Medical Birth Register and linked to the Abortion Register. Logistic regression analysis was used to estimate the risk (odds ratio [OR] and 95% confidence interval [CI]) of birth outcomes such as prematurity, low birthweight, perinatal death and small for gestational age (SGA).

RESULTS

Higher risk was determined for extremely preterm birth (OR 2.28; 95% CI 1.53-3.39) and very low birthweight (OR 1.62; 95% CI 1.22-2.16) in women having had late-induced abortion(s) (≥12 gestational weeks) compared with women having had early-induced abortion(s) (<12 gestational weeks); after adjusting for women's background characteristics, abortion method and interval between the pregnancies. When the analysis was limited to a single abortion, an increased risk was found for extremely preterm birth (OR 1.71; 95% CI 1.02-2.81). Higher risks were found for extremely preterm (OR 4.09; 95% CI 2.05-8.18) and very low birthweight (OR 2.65; 95% CI 1.61-4.35) among women with two or more late-induced abortions compared with those with two or more early-induced abortions. Worse outcomes were seen after a late-induced abortion compared to an early-induced abortion for both medically and surgically induced abortion.

CONCLUSIONS

The risk of subsequent adverse birth outcomes is very small if any, but the risk is higher with increasing gestational age at the time of induced abortion. Our study supports reduction of unintended pregnancy and offering abortion services without delay and as early in gestation as possible.