The Effect of Prior Term Birth on Risk of Recurrent Spontaneous Preterm Birth

Abstract

Objective: The objective of this study was to evaluate the effect of prior term birth on recurrent spontaneous preterm birth (sPTB) risk.

Study design: Retrospective cohort study of 211 women with prior sPTB, comparing women with and without prior term births. The primary outcome was recurrent sPTB <37 weeks. Analyses stratified by gestational age of prior sPTB and adjusted for confounders using multivariable logistic regression.

Results: The overall sPTB rate was 33.7%, with no statistical difference between women with and without prior term births (28.9 vs. 37.7%, p = 0.2). Among women with prior second-trimester loss (16-23^6/7 weeks), those with a term birth had a decreased sPTB rate (15.4 vs. 43.2%, p = 0.02), which persisted after adjusting for age and 17-α hydroxyprogesterone caproate use. For women with prior sPTB ≥24 weeks, there was no difference in sPTB with and without prior term births (29.5 vs. 26.6%, p = 0.7). A term birth as the most recent delivery lowered, but did not eliminate, the sPTB risk (19.1 vs. 36.4%, p = 0.1).

Conclusion: Prior term birth lowers the risk of recurrent sPTB for women with prior second-trimester loss, but not for women with prior sPTB ≥24 weeks. Women with prior preterm and term births should be counseled accordingly and all sPTB prevention strategies should be recommended.