Labor is induced by stimulating contractions of the uterus or ripening the cervix before the onset of spontaneous labor, usually because medical or obstetrical problems threaten the well-being of the mother or baby. Methods for inducing labor vary according to the situation and the obstetrician's practice.
To Induce or Not to Induce
The decision to induce labor is a serious one and should be made only after thoughtful consideration by you and your healthcare provider. Indeed, several authorities recommend you give informed consent before labor is induced. At the very least, you and your healthcare provider should have a frank discussion about the benefits and potential risks of inducing labor.
Of course, the baby is an important concern when considering induction of labor, especially the baby's ability to breathe once delivered. The baby's health may be threatened by remaining in the uterus under adverse conditions, such as hypertension in the mother or the premature rupture of membranes. The fundamental question to be addressed is whether induction of labor exposes you and your baby to more risk than remaining pregnant. With this question in mind, an elective induction should not be undertaken until the pregnancy has reached 39 weeks unless maturity of the baby's lungs has been confirmed by amniocentesis. Amniocentesis (a puncture through the abdomen to obtain amniotic fluid) can check the status of the baby's lungs by measuring the amount of certain lung proteins within the amniotic fluid.
Adverse Outcomes Associated with Inducing Labor
- Overstimulation and over-contraction of the uterus, limiting blood flow to the placenta and the baby.
- Failure to achieve labor and vaginal delivery resulting in the need for a cesarean section.
There are many reasons for inducing labor. The following list is not exhaustive but represents the most commonly accepted reasons:
- Premature Rupture of the Membranes. This is probably the single most common reason for inducing labor. Most cases occur near enough to the due date that induction of labor is reasonable. In general, labor will begin shortly after rupture of the membranes. If labor does not begin, induction may be appropriate to decrease the risk of intrauterine infection. If the membranes rupture before the 34 to 36th week of pregnancy, it may be better to delay delivery and keep the mother and fetus under careful observation.
- Hypertension (High Blood Pressure). Most cases of hypertension during pregnancy take the form of preeclampsia, but induction of labor is also considered for women with chronic, pre-existing high blood pressure even if preeclampsia has not been diagnosed.
- Suspected Fetal Jeopardy. Conditions such as suspected fetal growth restriction, low amniotic fluid volume (if membranes haven't ruptured), and abnormalities in the baby's heart rate may all be indications for inducing labor.
- Postdate Pregnancy. Pregnancy progressing beyond the due date, especially approaching 42 weeks, is often an indication for the induction of labor.
- Underlying Medical Conditions in the Mother. These include diabetes mellitus, renal disease (usually associated with hypertension), or lung disease such as pulmonary fibrosis or severe asthma.
- Fetal Demise. Labor is induced if the fetus is dead to avoid complications, such as blood loss, from retaining the fetus.
- Logistical Factors. Some women may be at risk for very rapid labor or may live far from the nearest medical facility, and the risk of delivering the baby at home or in the car may be greater than the physician and patient are willing to accept.
The accepted reasons for not inducing labor include:
- Placental Previa or Vasa Previa. The placenta or the umbilical cord is covering the cervix, the opening of the birth canal.
- Transverse Presentation of the Fetus. The baby is lying across the uterus, with the back or stomach pointed down toward the birth canal instead of the head.
- Breech Presentation of the Fetus. The baby's buttocks or feet are the closest part to the cervix, rather than the head.
- The umbilical cord has slipped through the cervix.
- The woman has had a previous classical cesarean section, which is a vertical incision on the uterus.
- The mother has an active genital herpes infection.
Induction of labor is not necessarily ruled out in women who have previously had the usual type of low transverse cesarean section (with a horizontal incision on the uterus) as long as contractions of the uterus can be carefully monitored.
A physician may hesitate to induce labor if the following conditions are present:
- Twins, or multiple births;
- Excess amniotic fluid;
- The baby's head is not down in the pelvis against the cervix; or
- Abnormalities in the baby's heart rate.
In any of these situations, the physician, using sound judgment, may elect to induce labor.
Suspected macrosomia (large-bodied fetus), is not an acceptable reason to induce labor. Studies show the decision to induce labor in these cases frequently results in a cesarean section. Elective induction, for the convenience of the physician or patient, is generally regarded as a poor idea and often increases the chance of having a cesarean section, especially for women having their first child.
Time Course of Induced Labor
The time from initiating an induction of labor to delivery varies considerably from woman to woman. Many variables work together to determine how long an attempt at induction of labor and delivery may take, including:
- Cervical status;
- Whether the mother has been pregnant before;
- How far along the pregnancy is; and
- Response to oxytocin (Pitocin).
In cases where the status of the cervix is not favorable and the need for delivery is not urgent, cervical ripening and attempted induction may take place over several days, with periods of rest. On the other end of the spectrum, a woman with two or more previous deliveries, whose cervix is in a very favorable condition, might deliver within a few hours after labor is induced.