OBJECTIVES:It is not known whether antenatal corticosteroids (ANS) can reduce the risk of retinopathy of prematurity (ROP). The aim of this study was to evaluate in a prospective cohort study the effect of ANS on ROP development and severity.METHODS:All infants consecutively admitted to 14 centres from 1.1.1992 to 31.12.1993, with a gestational age < or = 30 weeks, no congenital anomalies, and who survived to 6 months, were enrolled (N = 380). Mean birth weight of the cohort was 1157 g; mean gestational age was 28.4 weeks. ROP stage 1-2 developed in 82 neonates; ROP stage 3-3+ in 57. Only 70 neonates (18.4%) received ANS prophylaxis.RESULTS:ANS prophylaxis highly significantly reduced the risk of developing ROP [Odds ratio, (OR), 0.35; 95% confidence interval 0.17-0.71, logistic regression analysis], and that of severe (stage 3-3+) ROP (OR 0.07; 95% confidence interval: 0.02-0.34). Short gestation, low birth weight, bronchopulmonary dysplasia also were significantly associated with ROP development and severity; respiratory distress syndrome and not being treated with surfactant were significant risk factors for ROP severity.CONCLUSIONS:ANS prophylaxis protected both against ROP development and against severe forms of ROP. Prematurity and respiratory morbidity still represent independent risk factors for ROP.

Both the alveolar-arterial oxygen difference (AaDO2) and the arterial/alveolar ratio (a/AR) are widely used as indices of gas exchange, although data on their performance in neonates are lacking. This study was carried out to test 1) how stable these two indices are, and 2) how accurate is the prediction (based on a/AR) of changes in PaO2 when FiO2 is changed. 26 studies were done in 20 clinically stable ventilated neonates (median birth weight and gestational age: 1640 g and 30 weeks respectively). An arterial blood sample was taken from an indwelling catheter and AaDO2 and a/AR were calculated. The predicted PaO2 (based on a/AR) was compared with the actual PaO2 in a second sample obtained 26-80 minutes (median 40) after a change in FiO2 (mean 15%); AaDO2 and a/AR were calculated again. Results: mean baseline AaDO2 was 30.7 kPa (range 7.1-58.1); mean a/AR was 0.29 (0.085-0.69). Changes in AaDO2 were highly correlated with changes in FiO2 (r=0.94, P<0.0001, slope = 0.56 kPa/percent FiO2). Changes in a/AR were slightly correlated with changes in FiO2 (r=0.366, P<0.1). The mean difference between predicted and measured values of PaO2 after changes in FiO2 was 0.14 kPa (SD 3.15), yielding 95% confidence limits of −6.02 to 6.32 kPa. conclusions: 1) AaDO2 is highly dependent on FiO2, and should not be used to quantify gas exchange; a/AR is also (though to a lesser degree) sensitive to changes in FiO2; 2) the prediction of Pa02 based on a/AR calculation is accurate on average, but in individual cases the confidence limits are wide.

The gestational age of 302 neonates whose obstetric gestational age was known was assessed at birth using the Dubowitz method; it was obtained from Dubowitz score both graphically from a nomogram and by calculation from the corresponding equation. The values obtained graphically differed to a lesser extent from the obstetric gestational age than did the gestation derived algebraically. With infants small for gestational age (SGA) the difference between the methods was smaller and not significant. It is concluded that the concurrent knowledge of obstetric gestational age introduced a bias in the graphic step; this did not happen in SGA infants probably because in these cases the available information is sometimes less certain. These data demonstrate that even simple procedures are influenced by concurrent information; as a philosophical point about the interpretation of data in general, this study provides an empirical example of the 'theory-ladenness of facts' in medicine.