The study was designed to test the long-term influence of a low-dose oral contraceptive upon lactation and infant growth when treatment was initiated at day 90 postpartum. The contraceptive tested contained ethinyl estradiol 0.03 mg and levonorgestrel 0.15 mg. The control group was formed by women who chose non-hormonal contraception at the same postpartum time. Only cases who were in exclusive breast-feeding with a minimal infant daily weight increase of 20 g per day during the third month of age were included. The oral contraceptive group showed a significantly lower percentage of cases in full nursing from the 6th postpartum month and a significantly lower infant weight increase during the 4th month of age when compared to the control group. No differences were found in the absolute infant weight up to one year of age. No adverse side effects upon infant's health were detected. It was concluded that the oral contraceptive tested showed a moderate inhibitory influence upon lactation when treatment was initiated at day 90 postpartum.
PIP: The influence of a low-dose oral contraceptive (OC) on lactation and child growth when treatment is initiated at day 90 postpartum in fully nursing women was tested on 59 women using OCs and with 82 fully breastfeeding women (controls) choosing nonhormonal contraception (Emko foam and Copper T IUDS). The 2 groups were similar in age, weight, hemoglobin, and parity. The OC group received 1 pill/day containing ethinyl estradiol .03 mg and levonorgestrel .15 mg for 21 days followed by a 1-week pill-free interval. Mothers were instructed to give no food, liquid or solid, up to the 6th postpartum month unless prescribed by the pediatrician. Follow-up visits were monthly through 6 months and bimonthly to the end of the year. Infant weight increase was used as the most important objective indicator of adequate milk output. The OC group showed a lower proportion of full nursing cases for all intervals after treatment and a higher proportion where supplement was administered either by medical prescription or maternal decision. No significant differences were found between the 2 groups in time of weaning or in average absolute weight of exclusively breastfed infants during the 1st year. During the 1st month of treatment, infants in the OC group experienced a significantly lower weight increase than children in the control group. Total increase to the 6th month of age was 4881 +or- 939 g in the OC group and 5005 +or- 657 in the control group. An inhibitory effect of the low dose OC was deduced from the significantly lower percentage of cases in full nursing after initiation of treatment and from the significantly lower infant weight increases during the 1st month of pill use. The authors concluded that OCs do not represent a good choice during breastfeeding.