Racial differences in birthweight for gestational age and infant mortality in extremely‐low‐risk US populations

Abstract

Using national data, we develop and contrast the birth-weight percentiles for gestational age by infants of extremely-low-risk (ELR) White and African-American women and examine racial differences in the proportion of small-for-gestational-age (SGA) births. We then scrutinise racial variations in infant mortality rates of the infants of ELR women. We further compare the infant mortality rates of infants at or below the 10th percentile of birthweight for gestational age of each race group to determine whether infants with similar restricted fetal growth have comparable risks of subsequent mortality. Single live births, 34-42 weeks' gestation, to White and African-American US-resident mothers were selected from the 1990-91 US Linked Live Birth--Infant Death File (n = 4,360,829). Extremely-low-risk mothers were defined as: married, aged 20-34 years, 13+ years of education, multiparae, with average parity for age, adequate prenatal care, vaginal delivery, and no reports of medical risk factors, tobacco use or alcohol use during pregnancy. Marked racial variation in birthweight percentiles by gestational age was evident. Compared with ELR White mothers, the risk of an SGA infant was 2.64 times greater for ELR African-American mothers and the risk of infant mortality was 1.61 times greater. For the ELR group, the infant mortality rates of African-American and White infants at or below the 10th percentile of birthweight for gestational age of their respective maternal race group were essentially identical after controlling for gestational age. In conclusion, race differences in fetal growth patterns remained after controlling for risk status. Efforts to remove racial disparities in infant mortality will need to develop aetiological pathways that can explain why African-Americans have relatively higher rates of preterm birth and higher infant mortality rates among term and non-SGA infants.

Risk of adverse outcomes among infants of immigrant women according to birth-weight curves tailored to maternal world region of origin

“…26 The studies showed that, despite their higher rates of small-for-gestational-age infants based on a single standard, these infants did not have a higher risk of adverse outcomes. Whereas previous studies assessed the impact of maternal birthplace or ethnicity on small for gestational age, [24][25][26] we simultaneously evaluated the impact of maternal origin on large for gestational age and on a wide array of outcomes including neonatal death, thus generating a more complete picture.…”

US Birth Weight/Gestational Age-Specific Neonatal Mortality: 1995–1997 Rates for Whites, Hispanics, and Blacks

“…36 When compared with earlier reports, these data suggest that substantial improvements in neonatal mortality have occurred, particularly among LBW and preterm infants. 4,34,35,37 Notwithstanding, additional research is needed to determine how these improvements have affected the disparities in newborn survival between ethnic/racial groups and to identify where there has been a lack of progress. This study provides a foundation with which to examine these issues while providing reference data to assist physicians who work with newborns at the extreme limits of viability.…”

The Anatomy of a Disparity in Infant Mortality

“…"Small for gestational age" or "intrauterine growth retardation" can result in reduced birth weight for any given gestational age and may Figure 2 Cumulative percent of the racial disparity in neonatal mortality by birth weight category: United States, 1999. Source: (29) have different implications for subsequent morbidity and mortality (1). Although worthy of some analytic caution, birth weight continues to be used constructively as a general proxy for gestational age, particularly for birth weight categories contributing most heavily to disparate infant outcomes.…”