Determinants of birth weight in a low- and middle-income country: Sri Lanka Child Growth Cohort (SLCGC).

Background: Low birth weight (LBW), a substantial global public health problem, is associated with a range of both short-term and long-term consequences affecting human capital. The present study aims to investigate sociodemographic and pregnancy-related determinants of birth weight through analysis of Sri Lanka Child Growth Cohort (SLCGC) data. Methods: SLCGC is a retrospective cohort study that recruited 1875 children aged 12-24 months, born at term, using a stratified cluster sample across the country. The present analysis included 1563 mother-baby pairs, with data collected through the Child Health Development Record (birth weight, gestational age at birth, sex), Pregnancy Record (birth order, pre-pregnancy body mass index (BMI), gestational weight gain, diabetes, hypertension, haemoglobin), through interview (household assets to calculate wealth index, maternal age, education and employment, birth order, birth interval, supplements used) and through anthropometric measurements (maternal and paternal height). Univariate regression analyses were carried out to estimate the effects of a series of independent variables on birth weight, followed by a multiple regression analysis using the generalised linear model adjusting for confounders at a significance considered at p<0.05. Results: Mean birth weight was 2926 g (SD 406.9) and the LBW prevalence in term-born children was 12.5%. Adjusted analyses show that birth weight (g) of term-born children increases significantly with their parental height (maternal β=9.7, 95% CI 6.7 to 12.7, p<0.01; paternal β=2.4, 95% CI 1.4 to 4.5, p<0.01), pre-pregnancy BMI (β=19.2, 95% CI 15.2 to 23.1, p<0.01), gestational age at birth (β=131.3, 95% CI 114.5 to 148.0, p<0.01) and weight gain during pregnancy (β=20.9, 95% CI 16.9 to 24.9, p<0.01). Birth weight is significantly higher in males in contrast to females, the second or higher birth orders compared with first-born and those living in urban and rural sectors in contrast to the estate sector (plantations). Having diabetes during pregnancy has increased birth weight significantly, whereas hypertension reduced it. These associations were considered significant at p<0.05. Conclusion: Birth weight is determined by multiple factors. The consistent associations of parental height, pre-pregnancy BMI, weight gain during pregnancy, gestational age at birth and presence of diabetes and hypertension in pregnancy may have programmatic implications to achieve optimal birth weight in low- and middle-income countries.