While in the womb, a baby is exposed to many chemicals (hormones) present in the mother's blood stream. After birth, the infants are no longer exposed to these hormones. This may cause temporary conditions in a newborn.
Hormones from the mother (maternal hormones) are some of the chemicals that pass through the placenta during pregnancy. They affect the baby.
For example, during pregnancy high levels of the hormone estrogen are produced. This causes breast enlargement in the mother. It can have a similar affect in newborn boys and girls by the third day after birth. Such newborn breast swelling is temporary, but is a common concern among new parents. The breast swelling should go away by the second week after birth as the hormones leaves from the newborn's body. Do not squeeze or massage the newborn's breasts because this can cause an infection under the skin (abscess).
Maternal hormones may also cause some fluid to leak from the infant's nipples. This is called witch's milk. It is common and usually goes away within 2 weeks.
Newborn girls may also have temporary changes in the vaginal area.
These changes are common and should slowly go away over the first 2 months of life.
Newborn breast swelling; Physiologic leukorrhea