Calcium and phosphorus in milk of Brazilian mothers using oral contraceptives.

Objective: Oral contraceptives (OC) are the most efficient method of contraception and it is the most prescribed by doctors in developing countries. Therefore we studied the effects of combination pill and mini-pill on calcium and phosphorus in milk of breast-feeding mothers at different stages of lactation.
Methods: Fifty-four breast-feeding mothers made up three study groups: 33 mothers who had been advised by their doctors to use either combination pill (12), or mini-pill (21), as well as a control group of 21 mothers that used no hormonal contraceptives. All mothers completed a questionnaire and provided samples of milk before and after a measured period of observation. Mean duration of study was 76, 120, and 101 days, respectively for users of mini-pill, combination pill, and controls. Determination of calcium and phosphorus was done by inductively coupled plasma-atomic absorption spectrometry.
Results: Overall the decrease in milk concentrations of phosphorus (6%) and calcium (26.3%) during the study period was not influenced by OC treatment. Regression analyses which took into consideration length of treatment, socioeconomic status, number of children, duration of previous lactation, type of contraceptive, and age of mothers and repeated measurements (before and after OC) showed that milk calcium was significantly affected by stage of lactation (p=0.0013).
Conclusion: The use of hormonal contraceptive such as the combination pill (levonorgestrel 0.15 mg+ethynilestradiol 0.03 mg) and mini-pill (norethindone 0.35 mg) does not seem to affect the secretion of calcium and phosphorus in milk of mothers.