Almost half of Australian women of child-bearing age are overweight or obese, with a rate of 30-50% reported in early pregnancy. Maternal adiposity is a costly challenge for Australian obstetric care, with associated serious maternal and neonatal complications. Excess gestational weight gain is an important predictor of offspring adiposity into adulthood and higher maternal weight later in life. Current public health and perinatal care approaches in Australia do not adequately address excess perinatal maternal weight or gestational weight gain. This paper argues that the failure of primary health-care providers to offer systematic advice and support regarding women's weight and related lifestyle behaviours in child-bearing years is an outstanding 'missed opportunity' for prevention of inter-generational overweight and obesity. Barriers to action could be addressed through greater attention to: clinical guidelines for maternal weight management for the perinatal period, training and support of maternal health-care providers to develop skills and confidence in raising weight issues with women, a variety of weight management programs provided by state maternal health services, and clear referral pathways to them. Attention is also required to service systems that clearly define roles in maternal weight management and ensure consistency and continuity of support across the perinatal period.