Ecological breastfeeding and child spacing.

Until the 2nd and 3rd decades of this century, breastfeeding was essential for infant survival. In that period, spacing of children was generally about 2 years. Later, improved modified cow's milk preparations became commercially available and were well tolerated by most infants. As a result, near cessation of ecological breastfeeding occurred toward the middle of the century. The decline in ecological breastfeeding was associated with early postpartum ovulation and shortened child-spacing of about 1 year. The endocrinology of breastfeeding is now known in considerable detail. Prolactin is secreted promptly in response to nipple stimulation and is a reliable marker of the endocrine alterations occurring postpartum. Success of lactation in suppression of ovulation was found to occur when infants sucked frequently and when only small amounts of selected foods were introduced gradually after the infants were about 6 months of age.