A rise in arterial pressure above 140 mmHg systolic or 85 mmHg diastolic is pathological in pregnant women. Such changes may either reveal chronic
hypertension or constitute a purely gestational complication. The persistence or regression of abnormally high BP values 3 months after delivery retrospectively indicates whether the
hypertension was chronic or pregnancy-related. When BP values are very high (diastolic above 110 mmHg) the mother is exposed to vascular accidents and the most effective
anti-hypertensive drugs are required. In the more common moderate
hypertension, both the mother (
eclampsia) and the foetus (intra-uterine or
neonatal death, low birth-weight) are at risk. The risk is better predicted by
proteinuria and hyperuricaemia than by the BP values themselves, and whether
anti-hypertensive drugs are warranted is uncertain. Studied comparing patients with treated and untreated moderate
hypertension have yielded two valuable results: (1)
methyldopa administered to the mother is harmless to the foetus, and (2) abortion during the second trimester of pregnancy is probably prevented when
methyldopa is prescribed against chronic
hypertension. No study has yet afforded evidence that the use of
anti-hypertensive drugs in
gestational hypertension benefits the foetus. Further therapeutic trials and a better knowledge of the natural history and mechanisms of
hypertension in pregnancy are required before adequate management of this condition can be determined.