Induction of labor refers to techniques for stimulating uterine contractions to accomplish delivery prior to the onset of spontaneous labor. It is one of the most commonly performed obstetrical procedures in the United States. Between 1990 and 2011, the overall frequency of labor induction more than doubled, rising from 9.5 to 23.2 percent , and early term (in the 37th and 38th week of gestation) inductions quadrupled, rising from 2 to 8 percent . Some of this increase is related to a rise in the number of medically and obstetrically indicated inductions; however, it appears that marginally indicated and elective inductions account for a large proportion of the increase . Reasons for the increase in these inductions include the availability of better cervical ripening agents, patient and provider desire to arrange a convenient time of delivery, and more relaxed attitudes toward marginal indications for induction . Patient and provider concerns about the risk of fetal demise with expectant management near term or postterm have also contributed to the increased rate of induction.
Principles of induction of labor in women with an unscarred uterus will be discussed here. Issues regarding induction of labor in women who have had a previous cesarean delivery and methods of cervical ripening are reviewed separately. (See "Cervical ripening and induction of labor in women with a prior cesarean delivery" and "Techniques for ripening the unfavorable cervix prior to induction".)
Major societies, such as the American College of Obstetricians and Gynecologists (ACOG) [5,6], the National Institute for Health and Clinical Excellence (NICE) , and the Society of Obstetricians and Gynaecologists of Canada (SOGC) , have published guidelines for labor induction.
INDICATIONS FOR DELIVERY BEFORE ONSET OF LABOR
Obstetrical and medical indications — Delivery before the onset of labor is indicated when the maternal/fetal risks associated with continuing the pregnancy are thought to be greater than the maternal/fetal risks associated with early delivery . The only options are induction of labor or cesarean delivery. When there are no contraindications to labor and vaginal birth (see 'Contraindications to induction' below), induction of labor is generally preferred, given the increased maternal risks associated with cesarean delivery. (See "Cesarean delivery: Postoperative issues", section on 'Complications' and "Cesarean delivery: Postoperative issues", section on 'Long-term risks'.)
However, the magnitude of maternal/fetal risk of early delivery can rarely be determined with precision. The relative risk of delivery versus continuation of pregnancy is influenced by factors such as gestational age, presence/absence of fetal lung maturity, severity of the clinical condition, and cervical status. Although timely induction of women with some pregnancy complications has been recommended to improve maternal-fetal outcome [9,10], there is only limited high quality evidence establishing any benefits for specific medical and obstetrical indications for induction .