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

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.