Obesity in relation to pregnancy is becoming an increasing public health issue and 48% of women assigned to antenatal care in Sweden have overweight (BMI≥25) or obesity (BMI≥30). Obesity is associated with adverse perinatal outcomes, the risks increase with increasing BMI and excessive gestational weight gain (GWG) further increases the risks of adverse pregnancy outcomes. Lifestyle intervention can help pregnant women with obesity to limit their GWG. This study evaluated whether a low-budget antenatal lifestyle intervention programme, with emphasis on nutrition and physical activity, influenced GWG and maternal and perinatal outcomes for pregnant women with obesity. The study also evaluated which specific components of the intervention that had effect.