Planificación familiar durante el período de lactancia.

New mothers who do not breastfeed can choose any contraceptive method that would otherwise be suitable. Hormonal and barrier methods may be used in the immediate postpartum but IUDs should not be inserted until the later postpartum. Women who breastfeed require a contraceptive method that will not interfere with lactation or with the infant's growth and development. Although lactation itself provides a period of reduced fertility that is important in spacing births, great individual variability and lack of predictability about its duration means that women desiring maximum protection should begin contraception during lactation. The beginning of supplemental feeding and the return of menstruation are signs of increased fertility. It is difficult for methodological reasons to evaluate the effects of different contraceptive methods on lactation, which depends on many other variables as well. Many studies have failed to control other variables adequately, have used very small samples, or have failed to establish at what moment contraception is begun. There has been little uniformity in defining the duration or intensity of lactation. Available work however indicates that IUDs have no effect on lactation or infant growth. IUDs inserted in the early postpartum may be expelled or cause perforation. Barrier methods have never been carefully evaluated but theoretically they should not affect lactation. Methods based on periodic abstinence have no negative effects on lactation. The majority of studies on combined oral contraceptives (OCs) demonstrate negative influences on lactation, infant growth, and the composition of the milk, with effects apparently related to the dose and timing of the beginning of treatment. Combined OCs are contraindicated during lactation. If the woman wishes to use hormonal methods, the choice should be limited to those without estrogen and with minimal progestin doses so that the smallest possible steroid dose is passed to the infant. Low-dose oral formulations and progestin implants have not demonstrated any negative effects on lactation, but their use should be restricted. The passage of steroids to the child in breast milk remains an unresolved issue in progestin contraception. No health problems have been observed in children whose mothers have used progestin methods, but possible longterm effects on neuroendocrine mechanisms that regulate reproduction are not known. Large scale studies and follow-up are needed. Multicenter trials are currently underway with the natural hormone progesterone which is well tolerated and safe for the mother and almost inactive via the oral route. Administered in vaginal rings, it is effective and does not affect lactation or infant growth. It represents a promising method for the future.