In order to determine whether there is a correlation between meteorological factors and the occurrence of hypertensive disorders, vaginal bleeding during pregnancy and premature rupture of the fetal membranes, we stratified all the patients hospitalized with such complications between the years 1984 and 1988 by the months of occurrence, weather, humidity and heat. During this period, there were 276 women hospitalized with exacerbation of hypertension and toxemia, 349 because of vaginal bleeding during pregnancy and 35 women following premature rupture of the fetal membrane between 30 and 33 weeks of gestation. The occurrence of pre-eclampsia and exacerbation of pregnancy-induced hypertension was significantly increased in the winter months (p < 0.001).