High blood pressure (hypertension) is defined as a systolic blood pressure of 140 mmHg or more or a diastolic blood pressure of 90 mmHg or more. In the general population, a tight control of blood pressure reduces cardiovascular risks and is particularly important for people with diabetes or renal disease. Having high blood pressure during pregnancy is a complex clinical condition. Adverse effects include premature separation of the placenta (abruption), low birthweight, and perinatal death. Women who do not have regular antenatal care, those with severe uncontrolled hypertension and pre-eclampsia are more likely to have poor outcomes. A woman with mild-to-moderate hypertension could develop severe hypertension if not managed correctly. On the other hand, lowering blood pressure dramatically may reduce placental perfusion, which could lead to fetal growth restriction, without providing extra benefit to the mother. There is no consensus regarding a clear goal of adjusting blood pressure in pregnant women with mild-to-moderate hypertension.
This systematic review set out to compare the effects of 'tight' versus 'very tight' control of mild to moderate pre-existing or non-proteinuric gestational hypertension on pregnancy outcomes. It found insufficient evidence to determine which degree of control of blood pressure during pregnancy was more effective for improving outcomes for the mother and her baby. The review included two trials that studied 256 women. A blood pressure target of less than 130/80 mm Hg using methyldopa reduced the rate of admission to hospital during pregnancy. There was no evidence of a difference between tight and very tight control groups regarding severe pre-eclampsia, induction of labor and cesarean delivery and no cases of eclampsia or maternal deaths.