Perinatal outcomes of a large cohort of extremely low gestational age infants (twenty-three to twenty-eight completed weeks of gestation).

OBJECTIVES

To determine gestational age (GA)-specific mortality rates; the effects of GA, birth weight, sex, and multiple gestation on mortality rates; short-term morbidity for infants born at 23 to 28 weeks GA; and impairment rates at a corrected chronologic age of 18 months for those born at 23 to 25 weeks GA.

METHODS

A data base analysis was performed with a linked obstetric and a neonatal database. GA was determined by obstetric data and confirmed by early ultrasonography (available in 88%) on all births < 30 weeks GA at British Columbia's tertiary perinatal center from 1983 to 1989.

RESULTS

Of 1024 births occurring between 23 and 28 weeks GA, 911 were live born. The mortality rate decreased with increasing GA: 84% at 23 weeks; 57% at 24 weeks; 45% at 25 weeks; 37% at 26 weeks; 23% at 27 weeks; and 13% at 28 weeks GA. For each GA, mortality rate versus birth weight plots showed a decreasing mortality rate with increasing birth weight, except for infants who were large for GA. Male infants had a higher mortality rate than female infants (odds ratio, 1.8; confidence interval, 1.4 to 2.5). Twins fared worse than singletons with a decreasing effect from 24 weeks GA (odds ratio, 10.3) to no effect at 28 weeks GA. The median number of days supported by mechanical ventilation and the length of stay in the neonatal intensive care unit decreased markedly with increasing GA. Eighteen-month outcome of survivors between 23 and 25 weeks GA with 93% follow-up rate revealed an overall impairment rate of 36%, but 6 of the 9 surviving 23-week infants had major impairments.

CONCLUSIONS

The GA-specific perinatal outcome results of this large cohort provide information to assist in perinatal management decision making and for counseling parents prenatally.