Amniotic fluid infection, cytokines, and adverse outcome among infants at 34 weeks' gestation or less

We examined the hypothesis that amniotic fluid (AF) infection and elevated cytokine concentrations may cause neonatal injury beyond that expected solely from prematurity.

The effects of exposure to AF infection and elevated cytokine concentrations were measured in 151 infants born to afebrile women in preterm labor with intact membranes at less than or equal to 34 weeks' gestation. Amniotic fluid was collected by amniocentesis for culture and determination of tumor necrosis factor-alpha and interleukin-6. Cytokine concentrations, stratified by AF infection, were compared for three gestational age groups. We then examined the associations between a positive AF culture or elevated AF tumor necrosis factor-alpha concentration and adverse neonatal outcomes, adjusted for birth weight.

Amniotic fluid from 45 (30%) of 151 pregnancies had microorganisms, an elevated tumor necrosis factor-alpha concentration, or both. Amniotic fluid cytokine concentrations were significantly higher among women in preterm labor at less than or equal to 30 weeks, compared with 31-34 weeks. Nine of 11 infants who died at less than or equal to 24 hours of age had AF infection or elevated AF tumor necrosis factor-alpha. For the 140 surviving infants, AF infection and/or an elevated AF tumor necrosis factor-alpha was associated with respiratory distress syndrome (adjusted odds ratio [OR] 1.7), grade 3-4 intraventricular hemorrhage (adjusted OR 2.2), necrotizing enterocolitis (adjusted OR 1.8), and multiple organ dysfunction (adjusted OR 3.0).

Among infants born at less than or equal to 34 weeks to women who have intact membranes and are initially afebrile, those exposed to AF bacteria or cytokines have more adverse neonatal outcomes than unexposed infants of similar birth weight.