Role of gestational age and maternal biological factors in early term neonatal morbidity.

Background: The morbidity of early-term newborns (ETNBs) is associated with the immaturity of their organs and maternal biological factors (MBF). In this study, we determined the relationship between MBF and early-term birth. In addition, we assessed the role of gestational age (GA) and MBF in the morbidity of ETNBs compared with full-term newborns (FTNBs).

Methods: This retrospective cohort included ETNBs and FTNBs. The frequency of morbidities was compared between groups stratified by GA with the X² test or Fisher's exact test. The association of MBF with GA and morbidity was calculated using binomial regression models between the variables that correlated with the morbidity of the ETNBs using Spearman's correlation. A significance level of 5% was estimated for all analyses.

Results: The probability of morbidity at birth for ETNBs was 1.9-fold higher than for FTNBs (37.5% vs. 19.9%), as they required more admission to the neonatal unit and more days of hospitalization; the most frequent pathology was jaundice. The MBF associated with early term birth were hypertensive disorders of pregnancy (aRR = 1.4, 95% confidence interval (CI): 1.3-1.6), intrauterine growth restriction (aRR = 1.5, 95% CI: 1.3-1.6), and chronic hypertension (aRR = 1.6, 95% CI: 1.4-1.8). No association was found between MBF and morbidity at 37 and 38 weeks.

Conclusions: The morbidity among ETNBs is related to physiological immaturity. The adverse MBF favor a hostile intrauterine environment, which affects fetal and neonatal well-being.