[Previous medical or surgical abortions and subsequent risk of preterm birth: a birth cohort study].

Objective: To understand the association between medical abortion (MA) or surgical abortion (SA) and the risk of preterm birth (PTB) in subsequent pregnancy. Methods: The prospective cohort study was conducted in Ma'anshan, Anhui province. The information about demographic characteristics and previous MA or SA of 3 474 pregnant women were collected before 14 gestational weeks. Logistic regression analysis was conducted to compare the rates of preterm birth based on the history of previous MA or SA, and 3 256 live births were included in the analysis. Results: The PTB rate and spontaneous preterm birth (sPTB) rate were 4.12% (n=134) and 2.49% (n=81) respectively. Previous MA was associated with an increased risk of total PTB (RR=2.00, 95%CI: 1.04-3.85 for one MA and RR=3.58, 95%CI: 1.04-12.30 for two or more MAs) and sPTB (RR=2.51, 95% CI: 1.23-5.15). The risk of PTB in women with one SA (RR=0.67, 95%CI: 0.42-1.01) or more SA (RR=0.97, 95%CI: 0.51-1.85) did not differ significantly compared with the women with no history of SA. Conclusion: This study suggests that medical abortion could increase the risk of PTB or sPTB.