(HealthDay News) — Seasonal variation in vitamin D status may explain seasonal variation in hypertensive disorders of pregnancy, according to a study published online in Acta Obstetricia et Gynecologica Scandinavica.
Christine Rohr Thomsen, from Aarhus University Hospital in Denmark, and colleagues examined data from 50,665 previously healthy, nulliparous women with singleton pregnancies who gave birth between 1989 and 2010 at a single institution. Associations between seasonal variation in the risk for hypertensive disorders due to variation in sunlight exposure were examined.
The researchers found that 8.5% of women were diagnosed with a hypertensive disorder of pregnancy. Risk increased for women who conceived during spring and early summer; the risk then peaked during midsummer and decreased steadily during late summer and fall to reach the nadir by winter. Gestational hypertension, preeclampsia, and early-onset preeclampsia all had seasonal variation.
“This may support the existence of an association between vitamin D and the hypertensive disorders of pregnancy although more direct measurements of the vitamin D status at different times during pregnancy should be studied in relation to pregnancy complications in order to draw more certain conclusions,” the authors write.