Progestogen-only contraceptives during lactation: II. Infant development. World Health Organization, Task Force for Epidemiological Research on Reproductive Health; Special Programme of Research, Development, and Research Training in Human Reproduction.

Growth, development and health of infants whose mothers used progestogen-only contraceptives during lactation were examined in a prospective, non-randomized study that was carried out in seven centres in five countries (Egypt, Thailand, Kenya, Chile and Hungary). The results on development are reported here. Breastfeeding women requesting effective contraception were admitted to the study at six weeks postpartum. Infants of acceptors of progestogen-only methods (pill, DMPA, NET-EN or NORPLANT implants) and non-hormonal methods (IUD, barrier methods or sterilization) formed the study groups. The follow-up was at monthly intervals until the end of the first postpartum year. At each visit, the infant examination included, among other things, a set of developmental tests covering the following areas: gross motor, vision and fine motor, hearing, language and concept development, and self help and social skills. Participating in the study were 2466 mother-infant pairs. The comparisons between the study groups were carried out within centres using life table methods and Cox-model analysis having the time to first passing the test as the criterion. There were altogether 247 comparisons between the study groups. Thirty-two (13%) of these comparisons showed statistically significant differences: 20 differences showed that the infants in the progestogen-only groups passed the tests at an earlier age and 12 at a later age than infants in the non-hormonal groups. Since no consistent trends were observed across the centres, we conclude that in this study the progestogen-only contraceptives used during lactation did not adversely affect infant development.