Risk of recurrent spontaneous preterm birth: a systematic review and meta-analysis

OBJECTIVE To determine the risk of recurrent spontaneous preterm birth (sPTB) following sPTB in singleton pregnancies. DESIGN Systematic review and meta-analysis using random effects models. DATA SOURCES An electronic literature search was conducted in OVID Medline (1948-2017), Embase (1980-2017) and ClinicalTrials.gov (completed studies effective 2017), supplemented by hand-searching bibliographies of included studies, to find all studies with original data concerning recurrent sPTB. STUDY ELIGIBILITY CRITERIA Studies had to include women with at least one spontaneous preterm singleton live birth (<37 weeks) and at least one subsequent pregnancy resulting in a singleton live birth. The Newcastle-Ottawa Scale was used to assess study quality. RESULTS Overall, 32 articles involving 55 197 women, met all inclusion criteria. Generally studies were well conducted and had a low risk of bias. The absolute risk of recurrent sPTB at <37 weeks' gestation was 30% (95% CI 27% to 34%). The risk of recurrence due to preterm premature rupture of membranes (PPROM) at <37 weeks gestation was 7% (95% CI 6% to 9%), while the risk of recurrence due to preterm labour (PTL) at <37 weeks gestation was 23% (95% CI 13% to 33%). CONCLUSIONS The risk of recurrent sPTB is high and is influenced by the underlying clinical pathway leading to the birth. This information is important for clinicians when discussing the recurrence risk of sPTB with their patients.