A recent study (BD Reed et al. J Pediatr 2018; 197: 97-103) showed that prenatal antibiotic exposure was associated with lower rates of necrotizing enterocolitis (NEC) or death.
In this secondary analysis of a progressive study with 580 infants (<32 weeks) that were cared for in Level III neonatal intensive care units, the authors examined the outcomes of the neonates in relation to whether their mothers had prenatal antibiotics within 72 hours of delivery.
- Two-thirds of mothers received antibiotics w/in 72 hrs of birth, mainly ampicillin (37%) and azithormycin (26.4%). Most (~60%) of the mothers who received antibiotics received more than 1 antibiotic.
- In this cohort, NEC occurred in 7.5%, late onset sepsis (LOS) in 11.1%, and death in 9.6%. The combined outcome of any of these events occurred in 21.3% of study infants.
- Prenatal antibiotics were associated with a reduced risk of NEC (OR 0.28, CI 0.14-0.56), reduced risk of death (OR 0.29, CI 0.14-0.60) but not LOS (OR 1.59, CI 0.84-2.99). Thus, the first two outcomes were within the confidence limits but not LOS.
The authors indicate that their initial hypothesis was that maternal antimicrobials (w/in 72 hours of birth) would increase the risk of NEC but in fact provided a 3-fold protection and reduced the risk of death. The effects presumably would be mediated by changes in the infant microbiome related to infant’s exposure to microbial environment at birth and/or transplacental passage of antibiotics. The authors note that their study did not consider mothers to be in the exposure to antibiotics group if their only exposure was antibiotics at the time of cesarean section due to limited time to effect neonate. They did review this group and noted that if they were included in the exposure group that it would not have significantly changed the findings.
My take: This intriguing finding that NEC and death occurred less often in infant’s whose mothers received antibiotics prior to delivery needs further study as does the long-term effect.