induction of labor, an obstetric procedure in which labor is initiated artificially by means of amniotomy or administration of oxytocics. It is performed electively or for fetal or maternal indications. Elective induction is carried out for the convenience of the mother or the obstetrician, often to avert the possibility of delivery outside the hospital when labor is judged to be imminent and the mother is expected to have an unusually rapid birth. Elective inductions are performed less often now than in the past. Prerequisites for elective induction are a term gestation, a fetal weight of at least 2500 g, a cervix judged ready to dilate, a vertex presentation, and engagement of the presenting part of the fetus in the pelvis. Errors in the estimation of gestational age and fetal weight may result in the delivery of an unexpectedly immature or low-birth-weight infant. Indicated induction is performed when its risk is judged to be less than that of continuing the pregnancy in such conditions as premature rupture of the membranes, severe maternal diabetes, and intractable preeclampsia. Surgical induction is effected by amniotomy, often with stripping of the membranes and digital stretching of the cervix; it is very often carried out in conjunction with medical induction. Medical induction is achieved through the administration of oxytocin, almost always by IV infusion, in a carefully controlled manner using microdrip equipment or an infusion pump. Beginning with very small amounts of oxytocin in an IV solution, the dosage is increased by gradual increments of the rate or concentration of infusion until effective labor is established. With IV oxytocin inductions a secondary, piggyback infusion without medication is always attached to the tubing so that an unmedicated infusion can be maintained if oxytocin is stopped. Prostaglandins are more commonly used to induce labor in the second trimester, particularly for therapeutic abortions. Electronic fetal and uterine monitoring is usually instituted during induction of labor to prevent hyperstimulation of the uterus and fetal distress. Ideally induced labor mimics natural labor, but in practice it usually does not. Longer and harder contractions commonly occur. In addition to unexpected fetal immaturity, complications of induction of labor include umbilical cord prolapse after amniotomy, tumultuous labor, tetanic uterine contractions, rupture of the uterus, placental abruption, fetal maternal hypotension, water intoxication, postpartum uterine atony and hemorrhage, and fetal asphyxia, hypoxia, or death. If the induction fails to produce effective labor, cesarean section is often required to prevent the adverse sequelae of the procedures used in the induction. For this reason it is usually recommended that induction of labor not be attempted unless delivery must be accomplished to prevent severe fetal or maternal morbidity.
