The relevance of hypertension and oedema in pregnancy

The triad of severe pre-eclampsia is often described as a combination of hypertension, oedema and proteinuria. Hypertension alone arising in the second half of pregnancy however is not associated with any greater perinatal mortality or low birthweight than normotensive primigravidae and it is probable that this hypertension may be either physiological or a manifestation of essential hypertension or, in some cases, a mild form of pre-eclampsia. Oedema also does not necessarily signify abnormality. High weight gain, fluid retention or oedema is associated with a lower incidence of small babies, but with a higher incidence of pre-eclampsia. Considerable amounts of water retention can occur in normal pregnancy, either measured as an increase during pregnancy, or as a fall after delivery. The diuretics cyclopenthiazide, spironolactone and clopamide given prophylactically to high weight gain primigravidae did not prevent the onset of proteinuric pre-eclampsia, but caused the babies to be lighter in weight than those of controls. Sodium potassium and water content of leucocytes from primigravidae with proteinuric pre-eclampsia is the same as in mild pre-eclampsia and normal pregnancy. Although salt and water retention are common features of pre-eclampsia, they do not cause the condition and are not an essential part of it.