Researchers observed seasonal variations in the risk of the hypertensive disorders of pregnancy--including gestational hypertension and preeclampsia--in a study of Danish women. In the Acta Obstetricia et Gynecologica Scandinavica study, the highest risk for hypertensive disorders was seen in pregnancies conceived during spring and summer.
Of 50,665 women included in the study, 8.5% were diagnosed with a hypertensive disorder of pregnancy. There appeared to be increasing risk when conceiving during the spring and early summer, peaking midsummer, and subsequently decreasing steadily during the autumn to reach a low by winter. Seasonal variations in vitamin D levels may help to explain these findings.
Our results are of great interest, as vitamin D may have caused the observed seasonal variation in the hypertensive disorders. It has long been assumed that vitamin D affects the pathogenesis of hypertensive disorders of pregnancy--including preeclampsia--and our results support this hypothesis."
Christine Rohr Thomsen, lead author, Aarhus University Hospital, in Denmark
Thomsen, C. R., et al. (2020) Seasonal variation in the hypertensive disorders of pregnancy in Denmark. Acta Obstetricia et Gynecologica Scandinavica. doi.org/10.1111/aogs.13786.