Many mothers, especially those with co-morbidities, do not achieve exclusive breastfeeding (EBF) for the first 6 months, with the loss of multiple health benefits including enhanced infant nutrition. We wished to evaluate whether proactive lactation consultant telephone advice in the first month postpartum improved breastfeeding rates for up to 6 months. A prospective cohort observational study was performed. Mother groupings included the following: Control (CG,n= 379)—standard postnatal care; Exposure (EG,n= 386)—standard postnatal care delivered by lactation consultant telephone contact for the first 3 weeks postpartum and then follow-up calls at 1, 3 and 6 months postpartum to ascertain breastfeeding status. Sore nipples (24%) and fussy/unsettled behaviour (14–19%) were common EG concerns. EG EBF rates were higher at 1 month (65% vs. 53%;p< 0.001), 3 months (57% vs. 49%;p= 0.041) and 6 months (45 vs. 33%;p< 0.001). EG EBF rates across the 6 months were higher for infants admitted to the NNU (52.9% vs. 37.5%,p= 0.003), obese mothers (58.3% vs. 37.2%,p< 0.001), mothers with depression (60.8% vs. 43.4%,p= 0.036) and all birth modes. Proactive early lactation advice significantly prolongs EBF and consequently enhances infant nutrition overall, including for mothers at risk of early breastfeeding cessation.