Amniotic Fluid Infection, Cytokine Levels, and Mortality and Adverse Pulmonary, Intestinal, and Neurologic Outcomes in Infants at 32 Weeks' Gestation or Less

To what extent the risks of neonatal morbidities are directly related to premature birth or to biological mechanisms of preterm birth remains uncertain. We aimed to examine the effect of exposure to amniotic fluid (AF) infection and elevated cytokine levels on the mortality and pulmonary, intestinal, and neurologic outcomes of preterm infants, and whether these associations persist after adjustment for gestational age at birth. This retrospective cohort study included 152 premature singleton infants who were born at ≤ 32 weeks. AF obtained by amniocentesis was cultured; and interleukin-6 (IL-6) and IL-8 levels in AF were determined. The primary outcome was adverse perinatal outcome defined as the presence of one or more of the followings: stillbirth, neonatal death, bronchopulmonary dysplasia, necrotizing enterocolitis, intraventricular hemorrhage, and periventricular leukomalacia. Logistic regression analysis was adjusted for gestational age at birth and other potential confounders. In bivariate analyses, elevated AF IL-6 and IL-8 levels were significantly associated with adverse perinatal outcome. These results were not changed after adjusting for potential confounders, such as low Apgar scores, mechanical ventilation, and surfactant application. However, the independent effect of elevated cytokine levels in AF disappeared when additionally adjusted for low gestational age at birth; consequently, low gestational age remained strongly associated with the risk of adverse perinatal outcome. In conclusion, elevated levels of pro-inflammatory cytokines in AF are associated with increased risk of adverse perinatal outcomes, but this risk is not independent of low gestational age at birth. Culture-proven AF infection is not associated with this risk.