PIP: The effect of low-dose combined oral contraceptives (OCs) on lactation patterns during the 1st 6 months postpartum was investigated in 20 fully lactating, menstruating women. OC use was initiated on the 5th day of the 1st menstrual bleeding, and subjects were advised to take the pill during the longest interval between breastfeedings. There were no significant differences in milk yield between the subjects and nonmedicated lactating controls. However, in the 4th month the milk yield in the medicated group was significantly lower that that in the control group. The total protein content in both groups showed no significant difference. The fact that this investigation started after lactation was established may in part explain why lactation was maintained without inhibition. An estimated 10% of lactating women use OCs. Despite unresolved questions about the adverse effects of OCs on milk yield, family planning clinics continue to provide OCs to lactating women because of concern that these women may either discontinue breastfeeding in order to use OCs or use no contraception. Future studies should investigate the secretion of hormones in breastmilk, the effect of low-dose combined OCs on amenorrheic lactating women, and the duration of lactation.