Serum cortisol and vitamin D status are independently associated with blood pressure in pregnancy

The aim was to study if serum cortisol during pregnancy was associated with blood pressure and development of gestational hypertensive disorders. Additionally, associations between 25-hydroxyvitamin D (25OHD) and cortisol, including confounding effects and interactions in their relation to blood pressure were investigated. In total, 1413 pregnant women from the prospective Swedish GraviD cohort were included. Serum was collected in the first (T1) and third trimester (T3) and analyzed for 25OHD by liquid chromatography mass spectrometry and cortisol using an electro-chemiluminescence immunoassay. The main outcome measures were T1 blood pressure and development of gestational hypertensive disorders (gestational hypertension or preeclampsia). Gestational hypertensive disorders were defined as new onset hypertension, with or without proteinuria, after gestational week 20. Mean ± SD cortisol increased significantly from T1 to T3 (312 ± 123 vs. 659 ± 201 nmol/L, p < 0.001) and this increase was influenced by ethnicity. Serum concentrations of cortisol and 25OHD correlated in both T1 (B = 0.35, p < 0.001) and T3 (B = 0.30, p < 0.001). Cortisol and 25OHD were positively associated with T1 blood pressure, and there were non-significant trends for associations with gestational hypertensive disorders. Cortisol and 25OHD did not display any confounding effect or effect modification in their relationships with blood pressure. In conclusion, there was a positive correlation between serum cortisol and 25OHD in both early and late pregnancy. Both cortisol and 25OHD were positively associated with early pregnancy blood pressure. These results imply that the two hormones might be on different paths in their relationship with blood pressure.