A National Short-Term Follow-Up Study of Extremely Low Birth Weight Infants Born in Finland in 1996-1997

PEDIATRICS V.107, N.1 Jan01

Electronic Article p. e2

• Very Low Birth Weight Outcomes of the National Institute of Child Health and Human Development Neonatal Research Network, January 1995 Through December 1996  [Below]

Received Jun 2, 2000; accepted Aug 10, 2000.

Viena Tommiska^*, Kirsti Heinonen^±, Sami Ikonen^§, Pentti Kero||, Marja-Leena Pokela^¶, Martin Renlund^{*, #}, Martti Virtanen^**, and Vineta Fellman^*

From the ^* Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland; ^± Department of Pediatrics, University of Kuopio, Kuopio, Finland; ^§ Department of Pediatrics, University of Tampere, Tampere, Finland; ^|| Department of Pediatrics, University of Turku, Turku, Finland; ^¶ Department of Pediatrics, University of Oulu, Oulu, Finland; the ^# Department of Obstetrics and Gynecology; and the ^** National Research and Development Center for Welfare and Health, Helsinki, Finland.

Objectives.  The aims of this prospective nationwide investigation were to establish the birth rate, mortality, and morbidity of extremely low birth weight (ELBW) infants in Finland in 1996-1997, and to analyze risk factors associated with poor outcome.

Participants and Methods.  The study population included all stillborn and live-born ELBW infants (birth weight: <1000 g; gestational age: at least 22 gestational weeks [GWs]), born in Finland between January 1, 1996 and December 31, 1997. Surviving infants were followed until discharge or to the age corresponding with 40 GWs. National ELBW infant register data with 101 prenatal and postnatal variables were used to calculate the mortality and morbidity rates. A total of 32 variables were included in risk factor analysis. The risk factors for death and intraventricular hemorrhage (IVH) of the live-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% and 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. Neonatal 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 hours, 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 rate of IVH grades II through IV and NEC with bowel perforation decreased with increasing gestational age, but the incidence of RDS did not differ significantly between GWs 24 to 29. A total of 5 infants (2%) needed a shunt operation because of posthemorrhagic ventricular dilatation. Two hundred eleven ELBW infants (40% of all and 60% of live-born infants) survived until discharge 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. Neurological status was considered completely normal in 74% of the surviving infants. The proportions of infants born at 22 to 23, 24 to 25, 26 to 27, and 28 to 29 GWs with at least one disability (ROP, oxygen dependency, or abnormal 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 primary risk factor for IVH grades II through IV was RDS. Low 5-minute Apgar scores predicted poor prognosis, ie, death or IVH, and antenatal steroid treatment to mothers with threatening premature labor seemed to protect infants 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 found in morbidity, ie, oxygen dependency and ROP rates. Differences in perinatal (79% vs 45%) and neonatal (59% vs 32%) mortality rates were found between 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 improved rapidly with increasing maturity. The clear regional and hospital level differences detected in survival rates and in short-term outcome of ELBW infants emphasizes that the mortality and morbidity rates should be continuously followed and that differences should be evaluated in perinatal audit procedures. However, before the overall outcome of ELBW infants can be evaluated, the results of long-term follow-up and the effects of a premature birth on the family should be taken into consideration. prematurity, perinatal mortality, neonatal morbidity, extremely low birth weight infants.

Very Low Birth Weight Outcomes of the National Institute of Child Health and Human Development Neonatal Research Network, January 1995 Through December 1996

PEDIATRICS V.107, N.1 Jan01

Electronic Article p. e1

Received Apr 4, 2000; accepted Aug 14, 2000.

From ^* Indiana University, Indianapolis, Indiana; ^± University of Miami, Miami, Florida; ^§ Women and Infants Hospital, Providence, Rhode Island; ^|| University of Tennessee at Memphis, Memphis, Tennessee; ^¶ University of New Mexico, Albuquerque, New Mexico; ^# Emory University, Atlanta, Georgia; ^** Biostatistics Center, George Washington University, Rockville, Maryland; ^±± National Institute of Child Health and Human Development, Bethesda, Maryland; ^§§ Yale University, New Haven, Connecticut; ^|| Case Western Reserve University, Cleveland, Ohio; ^¶¶ Harvard University, Boston, Massachusetts; ^## University of Alabama, Birmingham, Alabama; ^*** University of Texas Southwestern Medical Center, Dallas, Texas; ^±±± University of Cincinnati, Cincinnati, Ohio; ^§§§ Wayne State University, Detroit, Michigan; and || || || Stanford University, Stanford, California.

Objectives.  To determine the mortality and morbidity for infants weighing 401 to 1500 g (very low birth weight [VLBW]) at birth by gestational age, birth weight, and gender.

Study Design.  Perinatal data were collected prospectively on an inborn cohort from January 1995 through December 1996 by 14 participating centers of the National Institute of Child Health and Human Development Neonatal Research Network and were compared with the corresponding data from previous reports. Sociodemographic factors, perinatal events, and the neonatal course to 120 days of life, discharge, or death were evaluated.

Results.  Eighty four percent of 4438 infants weighing 501 to 1500 g at birth survived until discharge to home or to a long-term care facility (compared with 80% in 1991 and 74% in 1988). Survival to discharge was 54% for infants 501 to 750 g at birth, 86% for those 751 to 1000 g, 94% for those 1001 to 1250 g, and 97% for those 1251 to 1500g. The incidence of chronic lung disease (CLD; defined as receiving supplemental oxygen at 36 weeks' postmenstrual age; 23%), proven necrotizing enterocolitis (NEC; 7%), and severe intracranial hemorrhage (ICH; grade III or IV; 11%) remained unchanged between 1991 and 1996. Furthermore, 97% of all VLBW infants and 99% of infants weighing <1000 g at birth had weights less than the 10th percentile at 36 weeks' postmenstrual age. Mortality for 195 infants weighing 401 to 500 g was 89%, with nearly all survivors developing CLD. Mortality in infants weighing 501 to 600 g was 71%; among survivors, 62% had CLD, 35% had severe ICH, and 15% had proven NEC.

Conclusions.  Survival for infants between 501 and 1500 g at birth continued to improve, particularly for infants weighing <1000 g at birth. This improvement in survival was not associated with an increase in major morbidities, because the incidence of CLD, proven NEC, and severe ICH did not change. However, poor postnatal growth remains a major concern, occurring in 99% of infants weighing <1000 g at birth. Mortality and major morbidity (CLD, severe ICH, and NEC) remain high for the smallest infants, particularly those weighing <600 g at birth.  Key words:  very low birth weight, morbidity, mortality, National Institute of Child Health and Human Development Neonatal Research Network, prematurity, preterm delivery.