The effect of maternal hypertension on mortality in infants 22, 29weeks gestation

To evaluate the effect of maternal hypertension on mortality risk prior to discharge, in infants 22+0 to 29+6weeks gestational age.

We evaluated 88,275 North American infants whose births were recorded in Vermont Oxford Network centers between 2008 and 2011 Infants born between 22+0 and 29+6weeks gestational age were evaluated in 2-week gestational age cohorts and followed until death or discharge. Logistic regression was used to adjust for birth weight, antenatal steroid exposure, infant sex, maternal race, inborn/outborn, prenatal care and birth year.

21,896 infants were born to hypertensive mothers; 13% died prior to Neonatal Intensive Care Unit discharge compared to 20% of the 66,379 infants born to mothers without hypertension. After adjustment, infants had significantly lower mortality compared to preterm infants not born to hypertensive mothers, at all gestational ages examined (22/23: odds ratio (OR)=0.65 (95% Confidence Interval (CI): 0.55, 0.77; 24/25); OR=0.77 (95% CI: 0.71, 0.84); 26/27: OR=0.66 (95% CI: 0.59, 0.74); 28/29: OR=0.58 (95% CI: 0.51, 0.67). Additionally, births associated with maternal hypertension increase dramatically by gestational age, resulting in a larger proportion of births associated with maternal hypertension at later gestational ages.

Preterm birth due to any cause carries significant risk of mortality, especially at the earliest of viable gestational ages. Maternal hypertension independently influences mortality, with lower odds of mortality seen in infants born to hypertensive mothers, after adjustment, and should be taken into consideration as an element in counseling parents.