The effect of induced abortion on the risk of low birth weight

Abstract

Background: China accounts for a quarter of the total number of induced abortion worldwide. Induced abortion is considered as one of the risk factors for adverse pregnancy outcome in subsequent pregnancy. The effects of induced abortion on premature delivery were investigated in both China and western countries, and most of the studies showed that increased risk of preterm birth was associated with increasing number of induced abortion. However, the association between low birth weight (LBW) and multiple induced abortions is still controversial. Objectives: To explore the association between LBW and previous induced abortion history, and to investigate the effects of preterm birth on the association. Methods: This case-control study used data from the Neonatal Intensive Care Unit (NICU), Nan Fang Hospital, between December 2011 and June 2012. We recruited 402 LBW (less than 2500 g) infants as our case group and 407 normal weight infants as the control group. Chi-square test and t-test were used for descriptive analysis. Multivariate logistic regression was run to yield odds ratios (OR) of LWB for multiple induced abortion adjusting for sex, birth order, maternal previous diseases and age, antenatal care received, and inter-pregnancy interval. Mediation effect of preterm status was investigated. Results: We observed a higher proportion of women with multiple induced abortions in LBW group (18.4% versus 11.1%, p value=0.003). Mothers with previous multiple induced abortion were 68.3% (95% confidence interval (CI): 11.0% to 155.3%) more likely to have LWB infants, compared with those who did not have induced abortion history or only once. After adjustment also for preterm status, the adjusted OR reduced to 1.332 (95% CI: 0.682 to 2.602) and the association became non-significant. Mediation test confirmed that preterm status was a mediator factor between multiple induced abortion and LBW. Conclusion: Overall, multiple abortions had an effect on LBW mainly through shortening the gestational duration of infants. Either premature delivery or LBW, the effect of multiple abortions on subsequent pregnancy was confirmed in this study. To reduce the perinatal mortality and morbidity, it is not enough only through postpartum care for preterm birth and LBW. The prevention and intervention strategies are urgently needed for reducing the induced abortion rate.