A successful breastfeeding relationship with your newborn can begin within minutes of birth. Those first nursing sessions can teach your baby how to latch and suck and initiate milk production. On average, a woman's milk comes in two to five days after the baby's birth. Several signs and symptoms will make it clear that you have started lactating.
After birth, your breasts will still feel soft. At this point, they are full of colostrum, a thick, rich, yellow "pre-milk" that nourishes your baby and allows you both to adjust to breastfeeding. When lactation begins, your breasts will become firmer as they fill with milk. You will notice that your breasts look and feel fuller as well. In addition to the milk enhancing your breasts' fullness, your breasts feature extra blood vessels and fluid when you are nursing, according to WebMD.
When your milk first comes in, it is a hybrid of the thick yellow colostrum and the thin milk that resembles skim milk. This transitional milk lasts for about 10 to 14 days, according to KidsHealth, before becoming more mature milk. When your baby is nursing, you may notice this thin, white milk spilling from his mouth when he latches off. Seeing this milk is a clear sign that your breast milk has transitioned from colostrum.
Your full breasts might start to leak when your milk comes in. While your milk supply is dictated by your baby's demands and feeding schedule, you may notice an oversupply of milk when it first comes in. Several factors contribute to leaking during the first few weeks postpartum. Your breasts may simply leak because they are too full or in response to let-down. Leaking may also occur due to too much nipple stimulation or hormonal imbalances, according to La Leche League International. Leaking breasts make it clear that lactation has begun.
While it does not happen to all mothers, engorgement of the breasts can occur during early lactation. Engorgement goes beyond typical postpartum fullness. Breasts that are engorged may be swollen, painful and warm to the touch. (see Ref 3) You may notice that your nipples have flattened out, and you may even have a slight fever, according to WebMD. Infrequent or short feedings can lead to engorgement for some mothers when their milk comes in.