Is blood pressure 120-139/80-89 mmHg before 20 weeks a risk factor for hypertensive disorders of pregnancy? A meta-analysis

Abstract

Aim: Hypertensive disorders of pregnancy affect approximately 10% of pregnant women worldwide with serious fetal and maternal implications. Chronic hypertension is diagnosed prior to 20 weeks of gestation and affects 1.5% of pregnant women. The American College of Obstetricians and Gynecologists defines hypertension in pregnancy as a systolic blood pressure higher than 140 mmHg or a diastolic blood pressure higher than 90 mmHg. In real-world clinical practice, practitioners consider the cut-off of 140/90 mmHg as a marker of true hypertension in pregnancy and consider blood pressures lower than that as normal.

Methods: To assess the association between a lower range of blood pressures and the development of hypertensive disorders of pregnancy, we performed a meta-analysis of current published studies comparing the occurrence of hypertensive disorders of pregnancy in patients with blood pressures of 120-139/80-89 mmHg before 20 weeks to those with blood pressures<120/80 mmHg.

Results: We included 24 studies: 12362/106870 (11.6 %) patients with blood pressures of 120-139/80-89 mmHg, and 26044/463280 (5.6 %) with blood pressures lower than 120/80 mmHg, developed hypertensive disorders of pregnancy [risk ratio 2.85 (C.I. 2.47-3.3)] - test for overall effect: Z = 14.1 (p < 0.00001).

Conclusions: We showed evidence of poor pregnancy outcome in patients with blood pressure lower than the routinely accepted cut-off of 140/90 mmHg. Therefore, interventions to mitigate the risk of hypertensive disorders in pregnancy in women with blood pressures 120-139/80-89 mmHg should be planned in new clinical trials.

Keywords: Eclampsia; Hypertensive disorders of pregnancy; Preeclampsia; Pregnancy; Stage one hypertension.