Intersibling variability of retinopathy of prematurity in twins and its risk factors.

To study intersibling variability of retinopathy of prematurity (ROP) in twins and determine its risk factors. A retrospective chart review of twin neonates developing ROP at a tertiary center over a 5 year period (January 2004 to December 2008). Twin pairs with intersibling variability of ROP were retrieved based on one of the following criterion: (1) two-stage difference in ROP between siblings, (2) one sibling with treatable ROP and the other with spontaneously regressed ROP, or (3) one sibling with aggressive posterior ROP and the other with staged ROP. Babies with greater severity of ROP were included in group A (case group) and their siblings with less severity in group B (control group).The two groups were compared for birth weight, birth order and putative post-gestational risk factors. Thirty-five twin pairs developed ROP of which 28 pairs (80%) had severe intersibling variability. Twenty-one pairs with complete information about risk factors were analyzed. The birth weight of the case group was 1212.1 ± 248.3 g (mean ± SD) and control group 1172.1 ± 216.5 g (mean ± SD) (p = 0.33). In twelve of the 21 pairs the second born twin had more severe ROP. However, birth order was not a significant predictor (p = 0.664). Various post-gestational risk factors did not differ significantly between the two groups [oxygen administration (p = 1), sepsis (p = 0.625), exchange transfusion (p = 1), blood transfusion (p = 0.325), respiratory distress syndrome (p = 1), anemia (p = 0.125), apnea (0.375), neonatal jaundice (p = 1), patent ductus arteriosus (p = 0.5) and hypoglycemia (p = 1)]. The majority of the twins developing ROP had severe intersibling variability. Birth weight, birth order and post-gestational neonatal risk factor were not predictive of more severe ROP in a twin sibling.