Childbirth (also called labour, birth, or parturition) is the culmination of pregnancy, the emergence of a child from its mother's uterus. It can be considered the opposite of death, as it is the beginning of a person's life outside of the womb. Age is defined relative to this event in most cultures.
A typical human childbirth will begin the onset of the first stage of labour: contractions of the uterus, at first every 10-30 minutes and lasting about 40 seconds each. Occasionally the labour will begin with a rupture of the amniotic sac, the paired amnion and chorion ("breaking of the water"). The contractions will accelerate until they happen every two minutes. Each contraction dilates the cervix until it reaches 10 centimetres (4") in width.
The duration of labour varies wildly, but averages some 13 hours for women giving birth to their first child ("primiparae") and 8 hours for women who have already given birth.
Immediately after birth, the child undergoes extensive physiological modifications as it acclimatizes to independent breathing. Several cardiac structures start regressing immediately after birth, such as the ductus arteriosus and the foramen ovale.
The medical condition of the child is assessed with the Apgar score, based on five parameters. A "good start" refers to higher scores, while a child doing poorly with have low scores that do not improve rapidly over time.
Non-progression of labor (longterm contractions without adequate cervical dilation) is generally treated with cervical prostaglandin gel or intravenous synthetic oxytocin preparations. If this is ineffective, Caesarean section may be necessary.
Fetal distress is the development of signs of distress by the child. These may include rising or decreasing heartbeat (monitored on cardiotocography/CTG), shedding of meconium in the amniotic fluid, and other signs.
Non-progression of expulsion (the head or presenting parts are not delivered despite adequate contractions): this can require interventions such as vacuum extraction, forceps extraction and Caesarian section.
In the past, a great many women died during or shortly after childbirth (see puerperal fever) but modern medical techniques available in industrialized countries have greatly reduced this total.
