Neonatal sex and maternal factors associated with small-for-gestational-age neonates: A nationwide population-based study.

ABSTRACT

Background and Aims: Small-for-gestational-age (SGA) newborns have a higher risk of morbidity and mortality. Recognizing the risk factors for SGA helps raise early awareness of the issue and provides valuable insights for both healthcare providers and pregnant women. We aimed to identify determinants of SGA using population-based databases in Taiwan. Methods: Data were retrieved from the National Health Insurance, Birth Reporting, and Maternal and Child Health databases for this nationwide case-control study. Live births between 20 and 44 weeks of gestation from 2005 to 2014 were enrolled and linked to their mothers to determine maternal conditions during pregnancy. For every SGA newborn, four controls matched by gestational age and birth year were randomly selected. Multivariable logistic regression was used to identify risk factors for SGA, with adjusted odds ratios (aORs) and 95% confidence intervals (CIs) accounting for potential confounders and interaction terms. Results: A total of 158,405 live SGA births were identified, with 623,584 controls randomly selected. Independent risk factors for SGA included maternal age <20 years (aOR 1.68, 95% CI 1.62, 1.75); female sex in newborns (aOR 1.28, 95% CI 1.27, 1.30); socioeconomic deprivation (aOR 1.29, 95% CI 1.21, 1.38); hypertension (aOR 1.6, 95% CI 1.52, 1.67); kidney disorders (aOR 1.29, 95% CI 1.16, 1.44); thyroid disorders (aOR 1.13, 95% CI 1.09, 1.17); systemic lupus erythematosus (aOR 2.59, 95% CI 2.33, 2.89); antiphospholipid syndrome (aOR 2.08, 95% CI 1.64, 2.64); gestational hypertension (aOR 1.69, 95% CI 1.61, 1.76); pre-eclampsia (aOR 3.12, 95% CI 3.01, 3.25); and antepartum hemorrhage (aOR 1.05, 95% CI 1.03, 1.07) after adjustment for other covariates. Conclusions: SGA was associated with younger maternal age, female newborns, underlying comorbidities, and obstetric conditions. Gestational hypertension and pre-eclampsia were significant risk factors affecting infants of both sexes and all age groups and could mask the effects of maternal age and infant sex.