8 The Open Pediatric Medicine Journal, 2009, 3, 8-12 1874-3099/09 2009 Bentham Open Open Access Immaturity and Disease Severity are Independent Risk Factors to Develop Retinopathy of Prematurity K. Allegaert *,1 , S. Vanhaesebrouck 1 , C. Vanhole 1 and I. Casteels 2 1 Neonatal Intensive Care Unit, Division Women and Child, University Hospital, Herestraat 49, 3000 Leuven, Belgium 2 Department of Ophthalmology, University Hospital, Leuven, Belgium Abstract: Purpose: Document indicators of an increased risk to develop retinopathy of prematurity (ROP) in low birth weight (LBW, < 1500g) infants. Methods: Retrospective chart review. Neonatal characteristics collected were birth weight, gestational age (GA), CRIB (Clinical Risk Index for Babies) score, Apgar score and indicators of respiratory, circulatory and renal instability. Small for gestational age (SGA, i.e. < 10 th percentile GA) was registered while postnatal growth was also recorded as a dichotomous variable, whether or not 150% of the birth weight was reached on day 42 of life. Results: On 284 LBW infants, 248 (87%) survived until discharge. ROP (any stage) was documented in 74 (30%) survivors of whom 41 (17%) developed stage 3 ROP. Incidence of stage 3 ROP in < 1000g and ROP in 1000-1250 birth weight cohorts was 42% and 16% respectively with almost absence of any ROP in neonates with a birth weight > 1 250g. In a logistic regression model in 248 LBW survivors, both GA (OR 0.42) and CRIB score (OR 1.35) remained independent risk factors for stage 3 ROP, resulting in 90% of cases classified correctly. Conclusions: Stage 3 ROP is almost exclusively limited to neonates with a birth weight below 1000g and retinopathy (any stage) is almost absent in neonates with a birth weight > 1 250g. Immaturity, i.e. GA at birth and CRIB score, reflecting disease severity, are the most important risk factors to develop retinopathy. INTRODUCTION Retinopathy of prematurity (ROP) is a multifactorial disease with numerous risk factors either based on immaturity (gestational age, birth weight) or indicators of disease severity [1]. Such indicators besides birth weight or gestational age (GA) might be used to further discriminate the relative risk to develop ROP associated with a given GA or birth weight [2, 3]. Prenatal as well as postnatal growth restriction, CRIB score, renal failure, dopamine administration and indicators of respiratory disease were reported in literature to be associated with an increased risk to develop ROP [4-14]. Observations on the simultaneous analysis of all these risk factors to unveil the most prominent risk factors are limited. O’Connor et al. recently reviewed the ophthalmological problems associated with preterm birth and hereby re- emphasized the long term consequences of retinopathy following preterm birth on visual function, eye growth and visual impairment in later life [15]. Others reported on the potential relevance of systematic screening and earlier surgical intervention to prevent further deterioration of retinopathy and visual function [16, 17]. Therefore, additional indicators might also enable caregivers to decrease the number of screening procedures in neonates at very low *Address correspondence to this author at the Neonatal Intensive Care Unit, Division of Women and Child, University Hospital Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium; Tel: 00-32-16-343210; Fax: 00-32-16-343209; E-mail: karel.allegaert@uz.kuleuven.ac.be risk or to develop secondary preventive strategies in neonates at high risk to develop major ROP [16]. Finally, these additional risk factors might help us to understand the underlying pathogenesis [1-3, 15, 18, 19]. To disentangle the various risk factors associated with ROP during later neonatal life, associations between perinatal variables and ROP were investigated in a cohort of low birth weight (LBW, < 1500g) neonates admitted in one single neonatal intensive care unit (NICU). MATERIALS AND METHODOLOGY Population A retrospective chart review in low birth weight infants (i.e. < 1500g) admitted in the neonatal intensive care unit, Gasthuisberg, during a 3 year’s period was performed. Infants had to be admitted in the unit within 6 hours after birth, needed to stay in the unit during at least the first week of life and ophthalmologic screening needed to be performed until full retinal vascularisation was documented to be included in this study. Neonatal characteristics collected at birth in these infants were birth weight, GA and Apgar score at five minutes. GA was calculated using the expected date of delivery based on an ultrasound performed before 20 weeks’ gestation, or if not available, was based on the last mother’s period and on neonatal clinical findings. Birth weight was documented on admission and compared with the birth weight of a Flemish cohort of preterm neonates as published by the Study Center of Perinatal Epidemiology to document SGA (< 10 th percentile for a given GA) [20]. Appropriated postnatal growth was registered as a dichotomous variable, defined as either or not an additional