Postpartum period  A postpartum (or postnatal) period begins immediately after the birth of a child as the mother's body, including hormone levels and uterus size, returns to a non-pregnant state. The terms puerperium or puerperal period, or immediate postpartum period are commonly used to refer to the first six weeks following childbirth. The World Health Organization (WHO) describes the postnatal period as the most critical and yet the most neglected phase in the lives of mothers and babies; most maternal and newborn deaths occur during the postnatal period. In scientific literature, the term is commonly abbreviated to P"x, where x" is a number; for example, "day P5" should be read as "the fifth day after birth". This is not to be confused with the medical nomenclature that uses G P to stand for number and outcomes of pregnancy (gravidity and parity). A woman giving birth in a hospital may leave as soon as she is medically stable, which can be as early as a few hours postpartum, though the average for a vaginal birth is one to two days. The average caesarean section postnatal stay is three to four days. During this time, the mother is monitored for bleeding, bowel and bladder function, and baby care. The infant's health is also monitored. Early postnatal hospital discharge is typically defined as discharge of the mother and newborn from the hospital within 48 hours of birth. The postpartum period can be divided into three distinct stages; the initial or acute phase, 6–12 hours after childbirth; subacute postpartum period, which lasts 2–6 weeks, and the delayed postpartum period, which can last up to six months. In the subacute postpartum period, 87% to 94% of women report at least one health problem. Long-term health problems (persisting after the delayed postpartum period) are reported by 31% of women. Various organizations recommend routine postpartum evaluation at certain time intervals in the postpartum period. The first 6 to 12 hours after childbirth is the initial or acute phase of the postpartum period. During this time the mother is typically monitored by nurses or midwives as complications can arise in this period. The greatest health risk in the acute phase is postpartum bleeding. Following delivery the area where the placenta was attached to the uterine wall bleeds, and the uterus must contract to prevent blood loss.