Association between breastfeeding and neurodevelopmental outcomes after late preterm birth.

To test the hypothesis that breastfeeding is associated with improved neurodevelopmental outcomes among children delivered late preterm. Secondary analysis of a prospective, follow-up study of ≥6-year-old children enrolled in the Antenatal Late Preterm Steroid (ALPS) Trial, a multicenter study that assessed betamethasone administration in pregnancies deemed to be at imminent risk of late preterm birth (34-36 weeks). Term births and those with missing breastfeeding data were excluded. The primary exposure was breastfeeding (exclusive or partial) at 3 months of life collected via maternal interviews. Any breastfeeding at 6 months was examined as a secondary exposure. The primary outcome was cognitive function at age ≥6, measured by the Differential Ability Scales, 2nd Edition (DAS-II) core components of the General Conceptual Ability (GCA) that includes verbal, non-verbal reasoning, and spatial abilities. Secondary outcomes included Gross Motor Function Classification System level, Social Responsiveness Scale, and Child Behavior Checklist scores. Multivariable analyses were adjusted for prespecified baseline characteristics (maternal age and education, gestational age at birth, child age, sex, tobacco use in pregnancy, ALPS study group, study center). Of 797 mothers included in the analysis, 414 (51.9%) were breastfeeding 3 months after giving birth. Participants who breastfed were older, of lower body mass index (BMI), and were more likely to be White, have a college degree, be married, have private insurance, and less likely to have used tobacco in pregnancy. Children of participants who breastfed were also older at follow-up. There were no differences in birth weight or gestational age at birth by breastfeeding status. The primary outcome, DAS-II GCA, was higher among children who were breastfed at 3 months, 100.5 ± 13.7 vs. 93.2 ± 13.2, mean difference of 7.27 (95% confidence interval [CI], 5.32, 9.22; adjusted mean difference, 2.54; 95% CI, 0.70, 4.37). In secondary analyses, differences in the overall GCA appeared to be driven by increased scores for spatial ability and nonverbal reasoning. There were no differences in secondary outcomes. Among children born late preterm at 34-36 weeks, breastfeeding (exclusive or partial) at 3 months of life was associated with improved neurodevelopmental outcomes at age 6 or older. Breastfeeding for ≥3 months was associated with a modest increase in GCA score (2.5 points; 0.17 SD), the clinical significance of which is likely greater at the population than individual level.