This behavioural support intervention trial will investigate the potential to increase exclusive breastfeeding rates in an urban Kenyan community through peer mother support delivered either by cell phone or through group meetings. It will follow a cohort of more than 800 women attending antenatal care at a large public hospital, and compare indicators of breastfeeding and infant and maternal health between groups receiving one or other type of peer mother support. The main part of the study will test the primary hypothesis that peer group and cell phone based support can both increase rates of EBF at 3 months by 20% relative to a control group.