This study was designed as a retrospective cohort study where patients given synthetic oxytocin during labor induction were considered as the exposed cohort, and patients not given oxytocin formed the non-exposed cohort. Four hundred of the 7465 children born at our maternity during 2006 were randomly selected. Information about breast-feeding was available for 316 of these children. Eventual confounding or adjustment factors were analyzed using stratified and multivariate analysis (logistic regression

Study population consisted of children born in our center (Hospital Materno-Infantil in Malaga) during 2006. Our hospital is a tertiary center of the Spanish national health system where were born 7465 children, representing 41.2% of all babies born in our province, from 7246 deliveries during that year 21. Random sample size was estimated at 400, with a 95% confidence levels and a 20% power, considering an expected RR of 0.82 22, a ratio between exposed and unexposed groups of 1.5, and a 20% loss. The sample selection was done by random sampling with the SPSS random number generator.

Once approval was obtained from the ethics and research committee of the hospital, recruitment and monitoring of selected cases was started during 2011. Data were collected by review of clinical records and interviews with the mothers (particularly to record breast-feeding type and duration). Patients were referred to the hospital for a semi-structured interview in which data were collected for type and duration of feeding. Clinical records were used as information sources for obstetric variables. Both the interviews and the review of medical records were blinded and conducted by the study authors in different days

Inclusion Criteria:

• children born in our center (Hospital Materno-Infantil in Malaga) during 2006

Exclusion Criteria:

-

Study population consisted of children born in our center (Hospital Materno-Infantil in Malaga) during 2006. Our hospital is a tertiary center of the Spanish national health system where were born 7465 children, representing 41.2% of all babies born in our province, from 7246 deliveries during that year