title: Multiple pregnancies and its relationship with the development of retinopathy of prematurity (ROP).
abstract: BACKGROUND
  The influence of multiple gestation on the occurrence of retinopathy of prematurity (ROP) is still not completely understood.
  
  
  OBJECTIVE
  To verify the incidence of any stage of ROP and threshold ROP in singletons and in multiple gestation among preterm infants.
  
  
  METHODS
  This was an institutional, prospective, and descriptive cohort study, which included preterm newborns with birth weight (BW) of 1500 g or less and/or gestational age (GA) of 32 weeks or less, as admitted to the neonatal units at Laranjeiras and Amparo Hospitals in Rio de Janeiro, Brazil, between January 2001 and July 2005, and whom remained hospitalized for at least 28 days. There were no exclusion criteria. Patients were divided into two groups: Group 1 included multiples; and Group 2 consisted of singletons.
  
  
  RESULTS
  A total of 159 infants that remained in neonatal unit care for at least 28 days were included in this study. Group 1 comprised 56 (35%) multiples; and Group 2 comprised 103 (65%) singletons. Mean BW was 1072 g ± 272 and 1089 g ± 282 in Groups 1 and 2, respectively (analysis of variance [ANOVA] P > 0.05). Mean GA among multiple gestation (Group 1) was 29 weeks ± 2.1; and 29 weeks ± 2.4 among singletons (Group 2) (ANOVA P > 0.05). Days in oxygen therapy ranged from 0 to 188 days. Median among Group 1 was 15 days, while median in Group 2 was 10 days (Kruskal-Wallis P > 0.05). Any stage ROP was detected in 66 (41.5%) of the whole cohort comprising 159 babies. Among the 56 multiples, 30 (53.6%) achieved any stage ROP, and among 103 singletons, 36 (35%) achieved any stage ROP (Chi-square test P < 0.05). Threshold ROP occurred in 12 (7.5%) of the 159 patients included. Three (5.3%) patients from Group 1 and nine (8.7%) patients in Group 2 reached threshold ROP needing laser treatment (Fisher's exact test P > 0.05).
  
  
  CONCLUSIONS
  This study showed higher frequency of any stage of ROP in twins and triplets but not regarding threshold disease. Because of the relatively small number of patients in this sample, other studies are necessary to determine if gemelarity plays a role in the occurrence of ROP.
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro RJ, Brazil.
authors.forename: Mário Martins
authors.initials: MM
authors.lastname: Dos Santos Motta
authors.forename: João Borges
authors.initials: JB
authors.lastname: Fortes Filho
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Coblentz
authors.forename: Claudia Amaral
authors.initials: CA
authors.lastname: Fiorot