Propranolol for the treatment of hypertension in pregnancy

Twenty-five women were treated with propranolol during 26 pregnancies complicated by hypertension. The fetal wastage, which had been 48 per cent before treatment with propranolol was reduced to 15.4 per cent, with one missed abortion and three stillbirths. Of the 22 liveborn infants 2 were small-for-dates but all 22 had Apgar scores of 9 or 10 at five minutes. There were no congenital anomalies in 25 viable infants and none of the 22 liveborn infants had clinical or laboratory evidence of hypoglycaemia. The blood pressure was controlled in 17 of 19 patients taking propranolol alone (40 to 160 mg/day) and in 6 of 7 taking propranolol with diuretics.

Renin, angiotensin and aldosterone in human pregnancy and the menstrual cycle

Aldosterone secretion is frequently, although not invariably, increased above the normal non-pregnant range in normal pregnancy. Substantial increases in plasma aldosterone concentration have also been demonstrated as early as the sixteenth week. In pregnancy, aldosterone secretion rate responds in the usual way to changes in sodium intake.

Plasma renin concentration is frequently, but not invariably, raised above the normal non-pregnant range. Plasma renin-substrate is consistently raised in pregnancy. Plasma angiotensin II has also been shown usually to be raised in a series of pregnant women.

A significant positive correlation has been shown between the maternal plasma aldosterone concentration and the product of the concurrent plasma renin and renin-substrate concentrations. This suggests that the increased plasma aldosterone in pregnancy is the consequence of an increase in circulating angiotensin II, which in turn is related to the level of both renin and its substrate in maternal blood. For these reasons, estimations of renin activity in pregnancy are of dubious value.

The increased renin, angiotensin and aldosterone concentrations may represent a tendency to maternal sodium depletion, probably mainly a consequence of the increased glomerular filtration rate. It is possible that the nausea and other symptoms of early pregnancy may be a consequence of this tendency to sodium depletion, with its attendant hormonal changes. In ‘pre-eclampsia’, renin and aldosterone values are generally slightly lower than in normal pregnancy. Human chorion can apparently synthesize renin independently of the kidney. The physiological significance of this remains at present obscure, but it seems unlikely that this source contributes much, if at all, to the often elevated maternal plasma renin.

Plasma renin, renin-activity and angiotensin II concentrations, and aldosterone secretion are increased in the luteal phase of the menstrual cycle.