Background: Retinopathy of prematurity (ROP) is a multifactorial disease, but little is known about its relationship with perinatal risk factors. We tested the hypothesis that the mode of delivery may be associated with threshold ROP as defined by CRYO-ROP.
Methods: We conducted a prospective, cohort analysis of a database of all extremely low birth weight (ELBW) neonates (= birth weight < 1000 g) admitted over a 8-year period from 1997 to 2004 to a large tertiary neonatal intensive care unit in a urban area of northern Italy and screened for ROP. Incidence of threshold ROP was calculated for the whole studied population. The definition of threshold ROP was as defined by the CRYO-ROP study. Univariate analysis was performed to look for significant associations between threshold ROP and several possible associated factors, and among them, the mode of delivery (vaginal delivery or caesarean section). When an association was indicated by p < 0.05, multiple logistic regression was used to determine the factors significantly associated with ROP.
Results: Enrolled ELBW neonates were 174, and 46 of them (26.4%) displayed threshold ROP. Threshold ROP occurred in 40.9% (27 of 66) of the neonates vaginally delivered and in 17.5% (19 of 108) of those born via caesarean section (R.R. 3.35; 95% CI 1.230-4.855; p = 0.008 at univariate analysis, and = 0.04 at multivariate logistic regression after controlling for birth weight, gestational age, intraventricular haemorrhage grade 2 or more, days on supplemental oxygen, systemic fungal infection). Birth by vaginal delivery was not significantly associated with other major sequelae of prematurity (intraventricular haemorrhage, bronchopulmonary dysplasia, necrotizing enterocolitis).
Conclusions: In our Institution birth by vaginal delivery is a significant and independent predictor of threshold ROP in ELBW infants. We suggest to consider closely ophthalmological surveillance for pre-term ELBW infants born this mode.