Low birth weight and its associated biopsychosocial factors over a 19-year period: findings from a national cohort study.

Background In Australia, 6.7% of babies (5.2% for singletons) are born low birth weight (LBW), and over the past decade, this figure has increased by 8%. Evidence regarding LBW has largely come from hospital-based cross-sectional studies, which are not representative, lack temporality and do not examine the potential predictors of LBW using a comprehensive theoretical framework. This study, therefore, examined predictors of LBW within a biopsychosocial framework, using a community-based representative prospective cohort with 19 years of data. Methods The study included 11 854 singleton babies born to 5622 women from the 1973 to 1978 cohort of the Australian Longitudinal Study on Women's Health. Results Among 5622 first births, 310 (5.5%) were reported as LBW. Maternal risk factors included pre-pregnancy underweight (aOR = 2.27, 95% CI: 1.43-3.62), chronic diabetes (aOR = 2.38, 95% CI: 1.14-4.95), gestational diabetes (aOR = 1.93, 95% CI: 1.27-2.94), chronic hypertension (aOR = 2.23, 95% CI: 1.50-3.33) and gestational hypertension (aOR = 2.44, 95% CI: 1.78-3.36). Among all births (N = 11 854), the overall LBW rate was 3.8% with a recurrence rate of 4.8%. Identified risk factors included menarche before 12 years (aOR = 1.57; 95% CI: 1.17-2.11), pre-pregnancy underweight (aOR = 2.25, 95% CI: 1.46-3.45), gestational diabetes (aOR = 1.74, 95% CI: 1.16-2.59), chronic hypertension (aOR = 2.01, 95% CI: 1.40-2.90) and gestational hypertension (aOR = 2.81, 95% CI: 2.05-3.84). LBW was less likely for second births (aOR = 0.39, 95% CI: 0.31-0.50) and third/above births (aOR = 0.49, 95% CI: 0.35-0.67) compared with the first births. Conclusion Increased nutrition counselling/supplementation for underweight women and interventions aimed at chronic disease prevention and management by using a multi-sectoral approach may be the key to the prevention of LBW.