Effect of oral contraceptives on composition and volume of breast milk.

Nitrogen and protein composition was determined in milk from women using oral contraceptives during lactation. Total nitrogen and nonprotein nitrogen as well as lactose and the individual milk proteins lactoferrin, alpha-lactalbumin, and serum albumin were analyzed before introduction of oral contraceptives and thereafter throughout the lactation period. Twenty-four hour milk volumes were registered by weighing the infant before and after each feeding. The four oral contraceptives used consisted of different combinations of d-norgestrel, megestrolacetate, and ethinylestradiol. Significant changes were observed between groups and controls for all parameters studied. However, the changes observed were generally within the physiological variation of normal breast milk. It is suggested that the use of oral contraceptives during lactation should be limited.