Cardiovascular risk factors prior to conception and the length of pregnancy: population-based cohort study

OBJECTIVE: To study the association of prepregnancy blood pressure, lipids, and glucose with length of pregnancy, and to assess whether the association between preterm delivery and later maternal cardiovascular disease may be due to common risk factors. STUDY DESIGN: Prospective study linking information of 3506 women in the HUNT Study with 4990 singleton births recorded in the Medical Birth Registry of Norway. RESULTS: Unfavorable prepregnancy levels of triglycerides, cholesterol, high-density lipoprotein-cholesterol, and glucose were associated with increased risk of preterm birth and shorter gestational length. Triglycerides above 1.6 mmol/L were associated with 60% higher risk of preterm birth (odds ratio, 1.6, 95% confidence interval, 1.0-2.5), compared with triglycerides below 0.7 mmol/L. Blood pressure was positively associated with risk of preterm birth and shorter gestational length, but these associations were substantially attenuated after adjustment for hypertensive disorders in pregnancy. CONCLUSION: Women with unfavorable cardiovascular risk factors before conception have excess risk of preterm birth.