The method of causing decreased fertility in a woman by nursing a child for a lengthy period (several years or more). In general, the longer a woman breastfeeds, the longer ovulation is delayed. For this method to work, a baby must be exclusively breastfed on demand, around the clock. Once other food and drinks are added to the infant’s diet, this method is not considered reliable. In addition, most breastfeeding women ovulate before their first postpartum menses and within 4 to 18 months after delivery.