Labor induction is the process or treatment that stimulates childbirth and delivery. Inducing labor can be accomplished with pharmaceutical or non-pharmaceutical methods. In Western countries, it is estimated that one quarter of pregnant women have their labor medically induced with drug treatment. Inductions are most often performed either with prostaglandin drug treatment alone, or with a combination of prostaglandin and intravenus oxytocin treatment.
Commonly accepted medical reasons for induction include:
Induction of labor in those who are either at or after term improves outcomes for the baby and decreases the number of C-sections performed.
Methods of induction
Methods of inducing labor include both pharmacological medication and mechanical or physical approaches.
Mechanical and physical approaches can include artificial rupture of membranes or membrane sweeping. The use of intrauterine catheters are also indicated. These work by compressing the cervix mechanically to generate release on prostaglandins in local tissues. There is no direct effect on the uterus.
Pharmacological methods include dinoprostone (prostaglandin E2), misoprostol (a prostaglandin E1 analogue), and intravenous oxytocin.
- Intravaginal, endocervical or extra-amniotic administration of prostaglandin, such as dinoprostone or misoprostol.Prostaglandin E2 is the most studied compound and with most evidence behind it. A range of different dosage forms are available with a variety of routes possible. The use of misoprostol has been extensively studied but normally in small, poorly defined studies. Only a very few countries have approved misoprostol for use in induction of labor.
- Intravenous (IV) administration of synthetic oxytocin preparations is used to artificially induce labor if it is deemed medically necessary. A high dose of oxytocin does not seem to have greater benefits than a standard dose. There are risks associated with IV oxytocin induced labor. Risks include the women having induced contractions that are too vigorous, too close together (frequent), or that last too long, which may lead to added stress on the baby (changes in baby's heart rate) and may require the mother to have an emergency caesarean section. There is no high quality evidence to indicate if IV oxytocin should be stopped once a women reaches active labor in order to reduce the incidence of women requiring caesarean sections.
- Use of mifepristone has been described but is rarely used in practice.
- Relaxin has been investigated, but is not currently commonly used.
- mnemonic; ARNOP: Antiprogesterone, relaxin, nitric oxide donors, oxytocin, prostaglandins
- "Membrane sweep", also known as membrane stripping, or "stretch and sweep" in Australia and the UK - during an internal examination, the practitioner moves their finger around the cervix to stimulate and/or separate the membranes around the baby from the cervix. This causes a release of prostaglandins which can help to kick-start labor.
- Artificial rupture of the membranes (AROM or ARM) ("breaking the waters")
- Extra-amniotic saline infusion (EASI), in which a Foley catheter is inserted into the cervix and the distal portion expanded to dilate it and to release prostaglandins.
- Cook Medical Double Balloon known as the Cervical Ripening Balloon with Stylet for assisted placement is FDA approved. The Double balloon provides one balloon to be inflated with saline on one side of the Uterine side of the cervix and the second balloon to be inflated with saline on the vaginal side of the cervix.
When to induce
The American Congress of Obstetricians and Gynecologists has recommended against elective induction before 41 weeks if there is no medical indication and the cervix is unfavorable. One recent study indicates that labor induction at term (41 weeks) or post-term reduces the rate of caesarean section by 12%, and also reduces fetal death.
Some observational/retrospective studies have shown that non-indicated, elective inductions before the 41st week of gestation are associated with an increased risk of requiring a caesarean section. Randomized clinical trials have not addressed this question. However, researchers have found that multiparous women who undergo labor induction without medical indicators are not predisposed to caesarean sections. Doctors and patients should have a discussion of risks and benefits when considering an induction of labor in the absence of an accepted medical indiction.
Studies have shown a slight increase in risk of infant mortality for births in the 41st and particularly 42nd week of gestation, as well as a higher risk of injury to the mother and child. Due to the increasing risks of advanced gestation, induction appears to reduce the risk for caesarean delivery after 41 weeks gestation and possibly earlier.
Inducing labor before 39 weeks in the absence of a medical indication (such as hypertension, IUGR, or pre-eclampsia) increases the risk of complications of prematurity including difficulties with respiration, infection, feeding, jaundice, neonatal intensive care unit admissions, and perinatal death.
Clinicians assess the odds of having a vaginal delivery after labor induction by a "Bishop Score". However, recent research has questioned the relationship between the Bishop score and a successful induction, finding that a poor Bishop score actually may improve the chance for a vaginal delivery after induction. A Bishop Score is done to assess the progression of the cervix prior to an induction. In order to do this, the cervix must be checked to see how much it has effaced, thinned out, and how far dilated it is. The score goes by a points system depending on five factors. Each factor is scored on a scale of either 0-2 or 0-3, any total score less than 5 holds a higher risk of delivering by caesarean section.
Criticisms of induction
Induced labor may be more painful for the woman. This can lead to the increased use of analgesics and other pain-relieving pharmaceuticals. These interventions have been said to lead to an increased likelihood of caesarean section delivery for the baby. However, studies into this matter show differing results. One study indicated that while overall caesarean section rates from 1990-1997 remained at or below 20%, elective induction was associated with a doubling of the rate of caesarean section . Another study showed that elective induction in women who were not post-term increased a woman's chance of a C-section by two to three times. A more recent study indicated that induction may increase the risk of caesarean section if performed before the 40th week of gestation, but it has no effect or actually lowers the risk if performed after the 40th week.
The most recent reviews on the subject of induction and its effect on Cesaerean section indicate that there is no increase with induction and in fact there can be a reduction.
The Institute for Safe Medication Practices labeled pitocin a "high-alert medication" because of the high likelihood of "significant patient harm when it is used in error." Correspondingly, the improper use of pitocin is frequently an issue in malpractice litigation.
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