Two years outcome of very pre-term and very low birthweight infants in Switzerland.

BACKGROUND

There are only few reports worldwide on the outcome of very pre-term infants and very low birthweight infants for a whole country. In Switzerland official population statistics are based on birthweight only, gestational age not yet being documented.

AIM

The aim of the present study was to assess the outcome at two years of age for a geographically defined high-risk neonatal population based on both birthweight and gestational age.

METHODS

All infants born in 1996 included in the Swiss Neonatal Network (a national anonymous registry established by the Swiss Society of Neonatology for liveborn infants before 32 completed gestational weeks or weighing less than 1500 g) were divided into three groups according to gestational age and birth weight: Group 1: born <32 completed gestational weeks and weighing =1500 g; group 2: born after 32 completed gestational weeks and weighing <1500 g; group 3: born <32 gestational weeks and weighing <1500 g. Information at 24 months corrected age about growth, neurological outcome, frequency of respiratory infections, prescription of antibiotics and medical consultations during this period was obtained from the paediatricians caring for the infants. Fair outcome was defined as survival without serious neonatal complications or abnormal neurological findings at 24 months corrected for prematurity.

RESULTS

723 infants were born alive in Switzerland between 1.1. and 31.12.1996 before 32 completed weeks or weighing less than 1500 g at birth. Mortality was 4.3% for a total of 163 infants in group 1 (<32 weeks, =1500 g), 4.6% for 108 infants in group 2 (>32 weeks, <1500 g) and 18.6% for 452 infants in group 3 (<32 weeks, <1500 g). 6.5% of group 1 survivors followed up to 24 months corrected age had a poor neurological outcome as compared to 9.3% in group 2 and 10.9% in group 3. Infants in group 1 needed antibiotics less often after hospital discharge (interquartile range IQR: 0-2 courses) than infants in group 2 (0-3 courses) and 3 (0-3 courses). Infants in group 2 suffered from fewer airway infections (interquartile range 2-5 times) than in group 1 (2-6 times) and 3 (1-7 times). Infants in group 3 needed more medical consultations (IQR 12-21) than those in group 1 (10-16) and 2 (11-16). The overall fair outcome at 24 months corrected age was 85.3% in group 1, 80.7% in group 2 and 59.6% in group 3. A close correlation between overall fair outcome and gestational age at birth on the one hand and with birthweight on the other can be observed.

CONCLUSIONS

This study gives estimates for mortality, poor and fair outcome at 24 months corrected age for very low birth weight infants (<1500 g) and for very pre-term infants (<32 completed gestational weeks). Gestational age is as important for predicting outcome as birthweight and should therefore be integrated into national statistics.