gynecology and obstetrics
Management of Normal Labor
Introduction
Labor consists of a series of rhythmic, involuntary or medically induced contractions of the uterus that result in effacement (thinning and shortening) and dilation of the uterine cervix. The World Health Organization (WHO) defines normal birth as follows: The birth is spontaneous in onset and low risk at the start of labor and remains so throughout labor and delivery. The infant is born spontaneously in the vertex position between 37 and 42 weeks of pregnancy. After birth, mother and infant are in good condition ( General reference ). The stimulus for labor is unknown, but digitally manipulating or mechanically stretching the cervix during examination enhances uterine contractile activity, most likely by stimulating release ofoxytocinby the posterior pituitary gland. Normal labor usually begins within 2 weeks (before or after) the estimated delivery date. In a first pregnancy, labor usually lasts 12 to 18 hours on average; subsequent labors are often shorter, averaging 6 to 8 hours. Management of complications during labor requires additional measures (eg, Induction of Labor , (See also Introduction to Intrapartum Complications .) 