A national short-term follow-up study of extremely low birth weight infants born in Finland in 1996-1997

Objectives. The aims of this prospective nationwide investigation were to e stablish the birth rate, mortality, and morbidity of extremely low birth we ight (ELBW) infants in Finland in 1996-1997, and to analyze risk factors as sociated with poor outcome. Participants and Methods. The study population included all stillborn and l ive-born ELBW infants (birth weight: <1000 g; gestational age: at least 22 gestational weeks [GWs]), born in Finland between January 1, 1996 and Decem ber 31, 1997. Surviving infants were followed until discharge or to the age corresponding with 40 GWs. National ELBW infant register data with 101 pre natal and postnatal variables were used to calculate the mortality and morb idity rates. A total of 32 variables were included in risk factor analysis. The risk factors for death and intraventricular hemorrhage (IVH) of the li ve-born infants as well as for retinopathy of prematurity (ROP) and oxygen dependency of the surviving infants were analyzed using logistic regression models. Results. A total of 529 ELBW infants (.4% of all newborn infants) were born during the 2-year study. The perinatal mortality of ELBW infants was 55% a nd accounted for 39% of all perinatal deaths. Of all ELBW infants, 34% were stillborn, 21% died on days 0 through 6, and 3% on days 7 though 28. Neona tal mortality was 38% and postneonatal mortality was 2%. Of the infants who were alive at the age of 4 days, 88% survived. In infants surviving >12 ho urs, the overall incidence of respiratory distress syndrome (RDS) was 76%; of blood culture-positive septicemia, 22%; of IVH grades II through IV, 20% ; and of necrotizing enterocolitis (NEC) with bowel perforation, 9%. The ra te of IVH grades II through IV and NEC with bowel perforation decreased wit h increasing gestational age, but the incidence of RDS did not differ signi ficantly between GWs 24 to 29. A total of 5 infants (2%) needed a shunt ope ration because of posthemorrhagic ventricular dilatation. Two hundred eleve n ELBW infants (40% of all and 60% of live-born infants) survived until dis charge or to the age corresponding with 40 GWs. The oxygen dependency rate at the age corresponding to 36 GWs was 39%, and 9% had ROP stage III-V. Neu rological status was considered completely normal in 74% of the surviving i nfants. The proportions of infants born at 22 to 23, 24 to 25, 26 to 27, an d 28 to 29 GWs with at least one disability (ROP, oxygen dependency, or abn ormal neurological status) at the age corresponding to 36 GWs were 100%, 62 %, 51%, and 45%, respectively. Birth weight <600 g and gestational age <25 GWs were the independent risks for death and short-term disability. The pri mary risk factor for IVH grades II through IV was RDS. Low 5-minute Apgar s cores predicted poor prognosis, ie, death or IVH, and antenatal steroid tre atment to mothers with threatening premature labor seemed to protect infant s against these. Some differences were found in the mortality rates between the 5 university hospital districts: neonatal mortality was significantly lower (25% vs 44%) in one university hospital area and notably higher (53% vs 34%) in another area. Furthermore, significant differences were also fou nd in morbidity, ie, oxygen dependency and ROP rates. Differences in perina tal (79% vs 45%) and neonatal (59% vs 32%) mortality rates were found betwe en secondary and tertiary level hospitals. Conclusion. Our study shows that even with modern perinatal technology and care, intrauterine and early deaths of ELBW infants are common. The outcome of infants born at 22 to 23 GWs was unfavorable, but the prognosis improve d rapidly with increasing maturity. The clear regional and hospital level d ifferences detected in survival rates and in short-term outcome of ELBW inf ants emphasizes that the mortality and morbidity rates should be continuous ly followed and that differences should be evaluated in perinatal audit pro cedures. However, before the overall outcome of ELBW infants can be evaluat ed, the results of long-term follow-up and the effects of a premature birth on the family should be taken into consideration.