Spontaneous preterm delivery (SPTB) may double a woman’s future risk of developing ischemic heart disease (IHD), stroke, or overall cardiovascular disease (CVD) over time, according to results of a new meta-analysis. While adding to previous such studies that suggest a link between preeclampsia and CVD, the researchers caution that future study is needed to determine how SPTB fits in clinically with traditional CVD risk factors.
The authors, from the Netherlands, analyzed 10 cohort studies with samples sizes ranging from 3,706 to 923,686 and follow-up ranging from 12 to 35 years. All of the studies were performed in northwestern European countries with predominantly white populations. The study dates ranged from 1966 to July 17, 2014 in Medline to 1980 to July 17, 2014 in Embase.
All of the studies in the meta-analysis assessed the relationship between SPTB and fatal or nonfatal IHD, stroke, or overall CVD. IHD, stroke, and CVD were assessed through linkage with national registries. Comparisons included were either of women with SPTB versus women with uncomplicated pregnancies or between women with preterm birth by any cause and those with uncomplicated pregnancies, with adjustment for preeclampsia and fetal growth restriction. At least 10 women with a history of SPTB birth had to be included and fatal or nonfatal IHD, stroke, or overall CVD had to be recorded as outcomes.
Evaluation of the studies was performed using the Newcastle-Ottawa quality assessment scale. Hazard ratios were pooled using a random-effects model. The authors found a two-fold increased risk of IHD (HR 1.38, 95% confidence interval [CI] 1.22-1.57), stroke (HR 1.71, 95% CI 1.53-1.91), and overall CVD over time (HR 2.01, 95% CI 1.52-2.65) in women with SPTB, which was consistent for different outcomes in those with a history of SPTB versus those with term delivery.
The strength of the meta-analysis, the researchers said, was inclusion of only high-quality cohort studies that used record linkage or medical records to assess for CVD. Confounders, however, differed between the studies. Limitations of the meta-analysis noted by the authors were lack of analysis of the influence of smoking during pregnancy, dating of gestational age based on last menstrual period, the high rate of heterogeneity in reported HR for CVD and IHD outcomes among studies, and potential for publication bias.