title: Seasonality of low birthweight in indigenous Australians: an increase in pre-term birth or intrauterine growth retardation?
abstract: We have analysed birthweights of 4,508 Aboriginal and Torres Strait Islander livebirths in the Kimberley region of Western Australia from 1981-93. Mean birthweight varied significantly according to month of birth (F(11) = 2.57, p = 0.003) and low birthweight babies were more common during the wet season. A significant increase in the proportion of very low birthweight (VLBW) babies was observed during the wet season compared with the dry season (OR 2.73; 95% CI 2.3-3.67; p < 0.001); whereas babies weighing 1,500-2,499 g were not significantly more common during the wet season (OR 1.06; 95% CI 0.96-1.17; p = ns). The results indicate that adverse environmental conditions may be associated with increased risk of VLBW. Since newborns weighing less than 1500 g are very likely to be pre-term (< 37 weeks' gestation), the findings also suggest that seasonality of birthweight may be due to an increase in pre-term births rather than an increase in intrauterine growth retardation. Further research is required to identify the underlying causes of an increase in VLBW babies during the wet season.
authors.affiliation: Department of Human Sciences, Loughborough University, Leicestershire, UK. e.k.rousham@lboro.ac.uk
authors.forename: E K
authors.initials: EK
authors.lastname: Rousham
authors.forename: M
authors.initials: M
authors.lastname: Gracey
mesh_terms: D001723:Birth Rate / Q000208:ethnology*; D005260:Female; D005317:Fetal Growth Retardation / Q000208:ethnology*; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007234:Infant, Premature; D007752:Obstetric Labor, Premature / Q000208:ethnology*; D016017:Odds Ratio; D011159:Population Surveillance; D011247:Pregnancy; D015995:Prevalence; D012307:Risk Factors; D012621:Seasons; D014904:Western Australia / Q000453:epidemiology; D000095283:Australian Aboriginal and Torres Strait Islander Peoples