Maternal cardiovascular disease risk factors as predictors of preterm birth in California: a case–control study

OBJECTIVE: To determine whether maternal cardiovascular disease (CVD) risk factors predict preterm birth. DESIGN: Case control. SETTING: California hospitals. PARTICIPANTS: 868 mothers with linked demographic information and biospecimens who delivered singleton births from July 2009 to December 2010. METHODS: Logistic regression analysis was employed to calculate odds ratios for the associations between maternal CVD risk factors before and during pregnancy (including diabetes, hypertensive disorders and cholesterol levels) and preterm birth outcomes. PRIMARY OUTCOME: Preterm delivery status. RESULTS: Adjusting for the other maternal CVD risk factors of interest, all categories of hypertension led to increased odds of preterm birth, with the strongest magnitude observed in the pre-eclampsia group (adjusted OR (aOR), 13.49; 95% CI 6.01 to 30.27 for preterm birth; aOR, 10.62; 95% CI 4.58 to 24.60 for late preterm birth; aOR, 17.98; 95% CI 7.55 to 42.82 for early preterm birth) and chronic hypertension alone for early preterm birth (aOR, 4.58; 95% CI 1.40 to 15.05). Diabetes (types 1 and 2 and gestational) was also associated with threefold increased risk for preterm birth (aOR, 3.06; 95% CI 1.12 to 8.41). A significant and linear dose response was found between total and low-density lipoprotein (LDL) cholesterol and aORs for late and early preterm birth, with increasing cholesterol values associated with increased risk (likelihood χ(2) differences of 8.422 and 8.019 for total cholesterol for late and early, and 9.169 and 10.896 for LDL for late and early, respectively). Receiver operating characteristic curves using these risk factors to predict late and early preterm birth produced C statistics of 0.601 and 0.686. CONCLUSION: Traditional CVD risk factors are significantly associated with an increased risk of preterm birth; these findings reinforce the clinical importance of integrating obstetric and cardiovascular risk assessment across the healthcare continuum in women.