Background Chorioamnionitis (CA) is associated with preterm birth and adverse neonatal outcomes. The correlation between stage of histological CA, and haematological parameters in the early postnatal period are incompletely defined.

Aim To examine the relationship between CRP and grade of CA in VLBW infants and any associations with neonatal outcomes.

Methods A retrospective review of consecutive infants born <32 weeks gestation or <1.5 kg at a single centre tertiary referral centre. CA on placental histology was reported as solely maternal inflammatory response (MIR) or both MIR and fetal inflammatory response (FIR). Demographics, haematological parameters and outcomes were recorded.

Results 509 infants were included and histological CA was found in 20% of placentas but 47.8% at <28 wks. CRP was raised above baseline (>0.3 mg/L) in 61.8% of infants with FIR, 64.7% of infants with MIR and 18.8% with no CA. CRP on day 1 >5 mg/L was specific for 90.9% of FIR, 3% of MIR, and 6.1% of infants no CA. CRP >10 mg/L was 100% specific for CA but not sensitive.. Advanced FIR on histology (funisitis) correlated significantly with higher CRP. A pathogen was isolated in 0.6% of CA and blood cultures were positive in 0.02% of preterm infant with the following outcomes: died (n = 6); FIR (n = 8); Funisitis (n = 5); High CRP (n = 5).

Conclusion CRP has good specificity (96% at 1 mg/L) for CA in preterm infants. Higher initial CRP levels in infants correlate with severity of histological CA.