Objective The objective of this study was to assess for the presence of newly acquired preterm birth (PTB) risk factors among primiparous women with no prior history of PTB. Design Case-control study. Setting Deliveries occurring within a large healthcare system from 2002–2012 Population Women with their first two consecutive pregnancies carried to ≥20 0/7 weeks gestation. Methods Those delivering the first pregnancy at term and the second preterm ≥20 0/7 and < 37 0/7 weeks (term-preterm cases) were compared to women with a term birth in their first two pregnancies (term-term controls). Social factors with the potential to change between the first and second pregnancies and intrapartum labour characteristics in the first pregnancy were compared between cases and controls. Main outcome measures Risk factors for term-preterm sequence. Results 38215 women met inclusion criteria. 1,353 (3.8%) were term-preterm cases. Cases and controls were similar with regards to race/ethnicity and maternal age at the time of the first and second deliveries. Cases delivered their second pregnancy approximately three weeks earlier (35.7 vs. 39.1, p<0.001). In multivariable models accounting for known PTB risk factors, women with a caesarean delivery in the first pregnancy (aOR=2.20; 95% CI 1.57–3.08), new tobacco use (aOR=2.33; 95% CI, 1.61–3.38), and an interpregnancy interval < 18 months (aOR=1.37; 95% CI, 1.21–1.55) were at increased risk of term–preterm sequence. Conclusion Caesarean delivery in the first pregnancy, new tobacco use, and short interpregnancy interval < 18 months are significant risk factors for term-preterm sequence. Women should receive postpartum counseling regarding appropriate interpregnancy interval and tobacco cessation.

Evidence from basic science studies supports a causative relationship between antiphospholipid antibodies (aPL) and recurrent early miscarriage (REM) (prior to 10 weeks of gestation). However, human studies have not consistently found a relationship between aPL and REM. Members of the Obstetric Task Force of the 14th International Congress on Antiphospholipid Antibodies performed a literature review of the association of aPL and REM and searched for clinical trials in women with REM who tested positive for aPL. Of the 46 studies that investigated the relationship between aPL and REM, 27 found a positive association, seven found no association, and the remaining 12 papers could not report an association (lack of control group). The main identified problems for such conflicting results were varying definitions of REM (two or three abortions, not necessarily consecutive; different gestational age at which pregnancy losses occurred); analysis of patients with previous fetal death (>10 weeks) in the same group of REM; and different definitions of "positive aPL" (cutoffs not following international recommendations; small number of studies confirmed persistence of positive aPL after six to 12 weeks). The 10 identified randomized trials with proposed treatments for women with REM who test positive for aPL also had heterogeneous inclusion criteria, with only one trial limited to subjects who would meet the current criteria for antiphospholipid syndrome (APS) by both clinical and laboratory criteria. Against this background, we conclude that the association between REM and aPL remains inconclusive and that the findings of treatment trials are at best inconsistent and at worst misleading. More convincing data are critically needed. Studies that identify, or at least stratify, according to international consensus criteria and include standardized core laboratory testing results are crucial if we are to establish an evidence-based association between aPL and REM and treatment recommendations.