Breastfeeding is the best way of feeding the baby for the first six months of life. However, in Portugal the abandonment rate of breastfeeding is very high during the baby first's months of life. The aim of this study was to assess prevalence of breastfeeding and to identify related factors during the six months after delivery, as socio demographic variables and life styles. We conducted a cohort study at the Maternity of the Hospital Santa Maria. A standard questionnaire was applied to 475 women after delivery, at three and six months postpartum. We studied socio demographics aspects, life styles and the way of feeding during the six months after delivery. Multivariate analysis was performed. The women studied (mean age of 29.8 +/- 5,4 years), 52.2% were primiparous, 86.1% were Caucasian, 40% had a high school degree and 33% had a University degree. Four hundred and sixty (96.8%) received prenatal care. The mean gestational age was 38.8 +/- 2 weeks and the birth weight was 3198.3 +/- 545.3 g. At the discharge 91% were breastfeeding (77% exclusively), 54.7% at third month and 34.1% at sixth month. The main causes pointed for abandoning breastfeeding were insufficient milk production, bad sucking and return to work. The milk formula introduction was in 68.6% cases by medical recommendation. The decision in maintenance breastfeeding at third and sixth months was correlated with a previous positive breastfeed experience, high educational level, healthy lifestyles, as non-smoking, regular physical activity, and information about advantage of breastfeed for mother health. Information about breastfeeding was received by media, friends, family and only 9% by health professionals. Fifty (13%) women had no information about breastfeeding. Although breastfeeding rate at discharge was high, there was an important rate of abandonment at third and sixth month. Healthy lifestyles, high educational level, a previous positive breastfeed experience had a positive influence in breastfeeding. Understanding attitudes towards pregnancy and breastfeeding can lead to new strategies for its promotion and maintenance.