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.