Objective: To determine the effects of oral contraceptive (OC) treatment on maternal iron and copper metabolism during lactation.
Design: Observational study.
Setting: Private and public clinics in Brazil.
Patient(s): Lactating mothers attending the family planning clinic of the University of Brasilia.
Intervention(s): The OCs used were a combination pill (0.15 mg of levonorgestrel and 0.03 mg of ethinyl estradiol) and a minipill (0.35 mg of norethidrone). Blood and breast milk samples were collected before and after a measured period of OC treatment.
Main outcome measure(s): Iron and copper concentrations were studied in the serum and breast milk of 54 breast-feeding mothers who had been advised by their physicians to use an OC, and in a control group.
Result(s): Regression analysis was performed using a model that took into consideration socioeconomic status, number of children, duration of previous lactation, type of OC, length of treatment, and age. Repeated measurements (before and after OC treatment) showed that only copper concentrations in breast milk were significantly affected by stage of lactation. During the study period, which varied from 2-15 weeks, the decline in iron concentrations in breast milk was negligible, whereas copper concentrations decreased by 50%.
Conclusion(s): The use of OCs does not appear to affect significantly the secretion of iron and copper in breast milk during the first 6 months of lactation.
PIP: This study examines the effects of oral contraceptive (OC) treatment on maternal iron and copper metabolism during lactation. The sample included lactating mothers attending the family planning clinic at the University of Brasilia. Participants were divided into 3 groups: 1) mothers who were taking combination pills (0.15 mg levonorgestrel and 0.03 mg ethinyl estradiol); 2) those who were taking minipills (0.35 mg norethindrone); and 3) a control group. Blood and breast milk samples were collected before and after a measured period of OC treatment. Results showed no significant effects of OC use on either iron or copper concentrations in serum during lactation. However, copper concentrations were significantly affected with the stage of lactation (iron, P = 0.9619; copper, P = 0.0002) as reflected in the multivariate model analysis. Therefore, the use of OCs does not appear to affect significantly the secretion of iron and copper in breast milk during the first 6 months of lactation.