Objective: To update our previous analysis of randomized controlled trials in pregnancy hypertension, which discerned that greater treatment-induced decreases in maternal mean arterial pressure (MAP) appear to adversely affect fetal growth.
Methods: We conducted an English-language computer search of MEDLINE, Hypertension in Pregnancy, the relevant Cochrane reviews, and the bibliographies of retrieved papers, review articles, and standard obstetric and toxicology texts. Metaregression analysis was used to compare the change in MAP from enrollment to delivery with birth weight.
Results: Seven new trials with 335 women were added to the 27 trials with 2305 women previously reported. No new trials reported on the frequency of small for gestational age infants. Treatment-induced mean difference in MAP was associated with lower mean birth weight (slope: -17.55 [SD 6.67], r2 = 0.19, Spearman's non-parametric p = 0.031, Pearson's parametric p = 0.013). Therefore, over the range of reported mean differences in MAP, a 10 mm Hg fall in MAP was associated with a 176 g decrease in birth weight, and 19% of the birth weight difference between trials could be explained by differential blood pressure control.
Conclusion: These results strengthen the association between blood pressure control and restricted fetal growth, and reinforce the need for new data to elucidate optimal antihypertensive use for mild to moderate pregnancy hypertension.