Low birthweight has been common among Aboriginal infants for generations. Birthweight is correlated within families due to the transmission of genetic and environmental factors. Another cause may be fetal programming, where a fetus’ response to a hostile uterine environment leads to poorer adult health and, in turn, a poorer uterine environment for her offspring.
Identifying a causal relationship between maternal and offspring birthweight is complex. However, we can gain insights using family-based approaches and Western Australia (WA) has a database of family relationships.
We used linked birth, hospital, and mental health records of 12,865 WA Aboriginal singletons born 1998-2011 whose mother linked to a WA birth record from 1980 onwards, and their parents’ records.
17% of births were small for gestational age. Using a linear regression model with a generalised estimating equation approach for offspring birthweight z-score (BWZ), the coefficient for maternal BWZ was 0.17, compared to 0.13 for paternal BWZ. The difference (0.03 [95% CI: -0.01, 0.08]) provides only limited support for the fetal programming hypothesis, particularly when issues such as non-paternity are considered. Other associations with offspring BWZ were much larger, including maternal smoking (-0.39 [95% CI: -0.45, -0.34]). In analysis of cousins with shared maternal grandparents (fixed-effects model), the mother-offspring association was fully attenuated (0.00 [95% CI: -0.05, 0.06]), suggesting transmission of maternal genetic and environmental factors alone may explain the association.
Compared to other risks, fetal programming appears to have a limited or no role in the persistence of low birthweights among Aboriginal infants.