Prehypertension in pregnancy may lead to smaller babies and a greater risk of stillbirth, according to results of a new Swedish study. Published in Hypertension, the findings shed light on the relationship between maternal blood pressure and fetal well-being and suggest that impaired maternal perfusion of the placenta contributes to small-for-gestational age (SGA) birth and stillbirth.
For the population-based study, the researchers looked at a cohort of 155,446 women without hypertension who had singleton deliveries at ≥37 weeks (n = 155,446). Using normotensive women (diastolic blood pressure [DBP] <80 mm Hg) as a reference, they calculated adjusted odds ratios (aOR) between prehypertension (DBP 80–89 mm Hg) at 36 weeks and the risks for SGA infants or stillbirth. They also estimated whether an increase in DBP from early to late pregnancy affected these risks.
Of the women in the study, 11% had prehypertension in late pregnancy. The condition was associated with an increased risk of an SGA infant (95% confidence interval [CI] 1.69; 1.51–1.90) and stillbirth (95% CI 1.70; 1.16–2.49). For each mm Hg rise in DBP from early to late pregnancy, risk of an SGA infant in a term pregnancy increased by 2.0% (95% CIs 1.5–2.8). No similar relationship was found between DBP increases in pregnancy and risk of stillbirth.
Prehypertension in late pregnancy, the researchers concluded, was positively associated with an increased risk of SGA infants and stillbirth and that increases in DBP during gestation also were correlated with rising risk of delivering an SGA newborn.