Hypertensive disorders of pregnancy include chronic hypertension, gestational hypertension, pre-eclampsia and chronic hypertension with superimposed pre-eclampsia. Pre-eclampsia complicates about 3% of pregnancies, and all hypertensive disorders affect about five to 10% of pregnancies. Secular increases in chronic hypertension, gestational hypertension and pre-eclampsia have occurred as a result of changes in maternal characteristics (such as maternal age and pre-pregnancy weight), whereas declines in eclampsia have followed widespread antenatal care and use of prophylactic treatments (such as magnesium sulphate). Determinants of pre-eclampsia rates include a bewildering array of risk and protective factors, including familial factors, sperm exposure, maternal smoking, pre-existing medical conditions (such as hypertension, diabetes mellitus and anti-phospholipid syndrome), and miscellaneous ones such as plurality, older maternal age and obesity. Hypertensive disorders are associated with higher rates of maternal, fetal and infant mortality, and severe morbidity, especially in cases of severe pre-eclampsia, eclampsia and haemolysis, elevated liver enzymes and low platelets syndrome.
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