Association of Late Preterm Birth and Size for Gestational Age With Cardiometabolic Risk in Childhood.

Importance: The long-term cardiometabolic consequences of late preterm birth (34-36 weeks' gestation) are not well understood. Objective: To assess whether late preterm birth and size for gestational age are associated with cardiometabolic risk (CMR) in childhood. Design, Setting, and Participants: This retrospective cohort study included 1742 children born in Ontario, Canada, between April 1, 2006, and September 30, 2014, and followed up until September 30, 2019. Data from children enrolled in The Applied Research Group for Kids (TARGet Kids!) primary care practice-based research network were linked to administrative health care data at ICES (formerly known as the Institute for Clinical Evaluative Sciences). Participants were excluded if they had conditions affecting growth (eg, failure to thrive or cystic fibrosis), any acute or chronic conditions (other than asthma and high-functioning autism), severe developmental delay, or families who were unable to communicate in English. Exposures: Late preterm birth, gestational age as a continuous measure, and size for gestational age. Main Outcomes and Measures: The primary outcome was composite CMR score (overall age- and sex-standardized z score of CMR components, including waist circumference, log triglyceride level, glucose level, systolic blood pressure, and high-density lipoprotein cholesterol level). Secondary outcomes were the individual CMR components. Multivariable linear regression analysis was used to separately evaluate the associations of late preterm birth, continuous gestational age, and size for gestational age with CMR at ages 3 to 12 years. Results: Among 2440 eligible children, 1742 (mean [SD] age, 5.6 [2.2] years; 951 boys [54.6%]) were included in the final cohort. Overall, 87 children (5.0%) were born moderately preterm (<34 weeks' gestation), 145 (8.3%) were born late preterm (34-36 weeks' gestation), 455 (26.1%) were born early term (37-38 weeks' gestation), and 1055 (60.6%) were born full term (≥39 weeks' gestation). Compared with children born full term, those born moderately preterm (adjusted β = 0.50; 95% CI, 0.24-0.75) and late preterm (adjusted β = 0.27; 95% CI, 0.06-0.47) had higher CMR scores. Each additional gestational week was associated with a 0.06 U (adjusted β; 95% CI, -0.08 to -0.03 U) decrease in CMR. Conclusions and Relevance: In this study, children born late preterm and moderately preterm had higher CMR. These results suggest that screening and early-life interventions for these children may prevent cardiometabolic outcomes.