The risk for recurrent preterm birth after prior preterm birth complicated by major fetal anomaly.

Major fetal anomalies (MFA) are a known risk factor for preterm birth (PTB), though the etiology of this is not well-studied, making counseling of these patients difficult. Thus, we sought to describe the rate of recurrent PTB in a second-observed pregnancy among persons with a history of PTB of an infant with a MFA in a first observed pregnancy, and to assess the difference in delivery timing between the first- and second-observed pregnancy. This was a retrospective cohort study of patients with a first-observed pregnancy complicated by MFA and a second-observed pregnancy in single healthcare system between 2013 and 2017. The primary outcome was recurrent PTB (PTB in second-observed pregnancy) and secondary outcomes were recurrent spontaneous PTB (SPTB), delivery gestational age (GA) in second-observed pregnancy, and difference in delivery GA between the first- and second-observed pregnancy. Recurrent PTB in the setting of prior PTB complicated by an MFA is common (∼1/4 patients), though median delivery timing for individuals who delivered preterm in the first-observed pregnancy was 6 weeks later in the second-observed pregnancy. These data suggest that PTB in the setting of MFA is a comparable risk factor to PTB in the absence of MFA.