Influence of chest/head circumference ratio at birth on obstetric and neonatal outcomes: The Japan environment and children's study

Abstract

Objectives: Some newborns that are not small-for-gestational-age (non-SGA, birthweight ≥10th percentile for a given gestational age) may have pathologic growth restrictions. This study examined the association of adverse obstetric and neonatal outcomes with chest/head circumference ratio at birth in non-SGA and SGA newborns. Methods: This study was a cross-sectional evaluation of data from a nationwide prospective birth cohort study, the Japan Environment and Children's Study. We analyzed 93 690 non-anomalous singletons born at 34–41 gestational weeks. We defined low, normal, and high chest/head circumference ratio as <10th percentile, 10th–90th percentile, and >90th percentile, respectively, according to the internally constructed chest/head circumference percentile chart. Modified Poisson regression was used to estimate adjusted prevalence ratios (aPR) for the outcomes studied. Results: Compared with non-SGA newborns with a normal ratio, those with a low ratio had an increased occurrence of low birthweight (1.75, 1.58–1.94 [aPR, 95% confidence interval]), cesarean delivery (1.34, 1.29–1.38), Apgar score <7 at 5 min (1.57, 1.14–2.17), respiratory complications (1.20, 1.04–1.39), and prolonged hospitalization (1.36, 1.30–1.42). In contrast, the high-ratio group had a lower rate of low birthweight (0.71, 0.59–0.86), cesarean delivery (0.82, 0.77–0.87), and prolonged hospitalization (0.83, 0.78–0.89). In SGA newborns, a low ratio was associated with increased aPRs for low birthweight, cesarean delivery, hypoglycemia, and prolonged hospitalization, whereas a high ratio showed no such association. Conclusions: Findings indicate that the chest/head circumference ratio at birth influence obstetric and neonatal outcomes regardless of the birthweight status.