Maternal Hypertension and Mortality in Small for Gestational Age 22- to 29-Week Infants

Infants born before 30 weeks gestational age (GA) to mothers with hypertension (HTN) experience lower rates of mortality and serious morbidities when corrected for maternal and infant characteristics. Growth restriction and maternal HTN are often associated. We sought to determine if small for gestational age (SGA) infants have similarly decreased mortality risk when born to mothers with HTN. We identified 6897 singleton SGA, 22 + 0 to 29 + 6 weeks GA infants born between 2008 and 2011, cared for at 578 North American centers in the Vermont Oxford Network. Chromosomal abnormalities and birth defects were excluded. Mortality rates prior to discharge were compared between 4317 HTN and 2580 comparison infants. Logistic regression was used to adjust for birth weight, infant sex, maternal race, inborn/outborn, antenatal steroid exposure, prenatal care, and GA. Small for gestational age HTN infants were older (mean: 26.9 [1.9] vs 26.6 [2.2] weeks; P < .001) and larger (HTN = 584 [159] g vs 562 [156] g; P < .001) than comparison infants. Death prior to discharge occurred in 29% of HTN and 43% of comparison infants. Univariate analyses revealed lower mortality for HTN infants (odds ratio [OR] = 0.54, 95% confidence interval [CI]: 0.48-0.60). After adjustment, mortality remained lower when compared to non-HTN infants (OR = 0.60, 95% CI: 0.52-0.69). Extremely preterm SGA infants face high rates of mortality. Although maternal HTN is associated with SGA, SGA infants born to mothers with HTN have decreased risk of mortality compared to non-HTN SGA infants, prior to and after adjustment for antenatal and maternal characteristics. This may reflect detrimental physiologic effects associated with alternative mechanisms for fetal growth restriction and is important for parental counseling.