The dilemma of less than 500 grams birth: epidemiologic considerations

Outcomes in extremely low birth weight (≤500 g) preterm infants: A Western Australian experience

BACKGROUND AND AIM

Extremely preterm (EP) infant survival has significantly improved with advanced neonatal care; however outcomes of infants born with birth weight (BW) ≤500 g remain poor. We aimed to review outcomes of this cohort in our institution.

METHODS

Retrospective study of all inborn preterm infants born at ≥22 weeks gestational age (GA) and weighing ≤500 g between January 2001-December 2017. Outcomes included short-term morbidity, mortality, neurodevelopmental impairment and growth up to five years of age.

RESULTS

Of a total 438 eligible infants, 92 livebirths were admitted to intensive care [median (range) GA: 24 (22-30) weeks; median (IQR) BW: 427.5 (380-499) grams]. Majority [78/92 (84.7%)] were small for gestational age (SGA). In 50% of non-survivors, median (IQR) age of death was 3.5 (1-17.5) days with no late deaths. Medical morbidities were common. Follow-up, including standardised cognitive assessments, was available for 41/46 (89%) infants. At a median age of 5.06 years, 17/41 (41.5%) had moderate-severe disability; non-statistically higher in SGA compared to appropriate for gestational age/AGA (48.6% vs. 33.3%) group. Cerebral palsy (4/41; 10%), deafness needing amplification (1/41; 2.4%) were noted. Weight (32/41, 78%) and height (27/41, 66%) of most children remained at >2 SD below normal.

CONCLUSIONS

In a cohort of preterm infants weighing ≤500 g at birth, 50% survived after admission to intensive care. Medical morbidities were common and 54% were free from moderate to severe disability at five years. SGA infants had higher rates (48.6%) of moderate to severe disability. Ongoing suboptimal growth in childhood is common.

Comment on “compromised birth outcomes and infant mortality among racial and ethnic groups”

Frisbie, Forbes, and Pullum (1996) show that it is meaningful to account for low birth weight, preterm delivery, and intrauterine growth-retardation when analyzing differences in compromised birth outcomes and infant mortality among racial and ethnic groups. I compare their findings for the 1987 U.S. birth cohort with findings for the 1988 U.S. birth cohort, using linked birth and infant death vital statistics from the National Center for Health Statistics. I focus on their calculation of fetal growth curves, which are highly at odds with the curves commonly used in the obstetric and pediatric literature. I compare birth outcome distributions and infant death probabilities using Frisbie et al. 's method and other standards. I conclude that Frisbie et al. 's method is not suited for the study of intrauterine growth-retardation at the population level because of the major flaws in gestational age measurement that exist in the type of data they use. An appropriate alternative is to apply a standard of normal intrauterine growth derived from antenatal estimation of fetal weight-for-gestational-age to the vital statistics data.