Seasonal variation in gestational blood pressure

Objective: To assess seasonal variability in antenatal blood pressure (BP). Methods: We studied 1919 pregnant women who contributed 21,119 antenatal BP measurements. Results: BP peaked in winter and reached a nadir in summer. After confounder adjustment, systolic BP was 1.0 to 1.7 mm Hg higher January to May, 0.6 mm Hg higher in September and October, and 0.8 mm Hg higher in November and December compared with August. After stratifying by overweight status, BP showed strong seasonal variability among lean women, whereas there were no seasonal trends among overweight women. Conclusion: Environmental factors may regulate gestational BP and may be relevant to seasonality of hypertensive disorders of pregnancy.