the process of labor and childbirth is known as
Childbirth Childbirth, also known as labour and delivery, is the ending of a pregnancy by one or more babies leaving a woman's uterus by vaginal passage or C-section.[4] In 2015 there were about 135 million births globally.[5] About 15 million were born before 37 weeks of gestation,[6] while between 3 and 12% were born after 42 weeks.[7] In the developed world most deliveries occur in hospital,[8][9] while in the developing world most births take place at home with the support of a traditional birth attendant.[10]
Adaptation to extrauterine life Perfusing its body by breathing independently instead of utilizing placental oxygen delivered via the umbilical cord is the first challenge of a newborn. At birth, the baby's lungs are filled with lung liquid, which is distinct from amniotic fluid.[1] When the newborn is expelled from the birth canal, its central nervous system reacts to the sudden change in temperature and environment.[2] This triggers it to take the first breath, within about 10 seconds after delivery.[2] With the first breaths, there is a fall in pulmonary vascular resistance, and an increase in the surface area available for gas exchange. Over the next 30 seconds the pulmonary blood flow increases and is oxygenated as it flows through the alveoli of the lungs. Oxygenated blood now reaches the left atrium and ventricle, and through the descending aorta reaches the umbilical arteries. Oxygenated blood now stimulates constriction of the umbilical arteries resulting in a reduction in placental blood flow. As the pulmonary circulation increases there is an equivalent reduction in the placental blood flow which normally ceases completely after about three minutes. These two changes result in a rapid redirection of blood flow into the pulmonary vascular bed, from approximately 4% to 100% of cardiac output. The increase in pulmonary venous return results in left atrial pressure being slightly higher than right atrial pressure, which closes the foramen ovale. The flow pattern changes results in a drop in blood flow across the ductus arteriosus and the higher blood oxygen content of blood within the aorta stimulates the constriction and ultimately the closure of this fetal circulatory shunt.