Amniotic fluid interleukin-6 and the risk of early-onset sepsis among preterm infants

High concentrations of interleukin-6 (IL-6) have been demonstrated in amniotic fluid (AF) from women with intra-amniotic infection. Recent studies have reported that IL-6 levels in AF were related to an increase in neonatal morbidity; moreover, higher IL-6 plasma levels have been observed in neonates with sepsis.

A cohort study was carried out at the National Institute of Perinatology in Mexico City. Inclusion criteria were the following: 1) preterm singleton pregnancy; 2) intact membranes at time of enrollment, and 3) written informed consent. Women with other complications of pregnancy were excluded. Newborn sepsis during the first 72 h was defined as early-onset sepsis. Amniotic fluid was obtained at the moment of delivery. Amniotic fluid IL-6 (AF IL-6) was determined by enzyme-linked immunoassays.

Ninety-three women met the criteria for enrollment in the study and 31 (33%) of their newborns had early-onset neonatal sepsis. The mean AF IL-6 in mothers of septic newborns was 5779 +/- 2804 pg/ml compared to 729 +/- 382 pg/ml in mothers with non-infected neonates (p < 0.001). AF IL-6 concentrations higher than 1250 pg/ml were significantly associated with early-onset sepsis (OR 33.3; 95% CI 9.4-117.3) (p < 0.001). Gestational age under 32 weeks was also associated with neonatal sepsis (OR 2.56; 95% CI 1.2-9) (p = 0.002). Women whose infants developed neonatal sepsis had a higher frequency of clinical chorioamnionitis (p = 0.02).

IL-6 determination in AF may be a useful indicator to identify neonates with higher risk of in utero bacterial infection.