History of induced abortion and the risk of preterm birth: a retrospective cohort study

Abstract

Objectives

To explore the relationship between a history of induced abortion and follow-up preterm birth.

Methods

We performed a retrospective cohort study of 27,176 women aged 19 to 48 years old in the city of Dongguan. Participants were divided into two groups according to the history of induced abortion. We used log-binomial regression to estimate adjusted risk ratios of preterm birth (gestation at less than 37 weeks) and early preterm birth (gestation at less than 34 weeks) for women with a history of induced abortion. Four models adjusted for different baseline data were used to verify the stability of the results. We also performed a subgroup analysis and mediation effect analysis to control for the influence of confounding factors and analyzed the relationship between the number of abortions and subsequent preterm birth.

Results

Our study included 2,985 women who had undergone a prior induced abortion. Women who reported having a prior induced abortion were more likely to have preterm births before 37 weeks and 34 weeks, with risk ratios of 1.18 (95% CI 1.02–1.36) and 1.65 (95% CI 1.23–2.21), respectively. The above associations were stable in all models. We also found that a history of induced abortion was independently associated with a higher risk of preterm birth and early preterm birth in the subgroups. After controlling for the indirect effect of demographic data, the direct effect of abortion history on follow-up preterm delivery was still significantly different. The higher the number of abortions, the greater the risk of subsequent preterm birth.

Conclusions

This study suggests that induced abortion increases the risk of subsequent preterm birth.

Keywords:

• Cohort study
• induced abortion
• preterm birth
• risk factors

Acknowledgements

The authors thank all the obstetricians, pediatricians, pathologists, statisticians and other participants involved in the birth defects monitoring program and NFPHEP in Dongguan City. The authors also thank Mr. Ri-Hui Liu for his great support and help in the statistical analysis and writing of this paper.

Ethics approval and consent to participate

This study was approved by the ethics committee of Dongguan Maternal and Child Health Care Hospital September 30, 2018 (No. [23] 2018). All participants signed informed consent before the examination.

Authors’ contributions

All the authors contributed a lot to this research. Conception and design of the study: YJY, JB, ZXJ, WSS, HWC. Gathering of data: YJY, JB, ZXJ, WSS, HWC; Analysis and interpretation of the data: HWC, YJY. Drafting of the manuscript: HWC, YJY; Critical revision of the manuscript: JB, ZXJ, WSS; Approval of the final version for publication: all the author.

Consent for publication

Not applicable.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Due to the policy, the original data of this study cannot be shared.

Additional information

Funding

This is not a funded research project so “not applicable.”