How Labor Is Induced

Your due date came and went a week and a half ago. Your telephone rings constantly and every time you answer it, a friend or relative exclaims, "You're still home!" These last few days seem longer than the previous nine months. Your practitioner told you at this week's appointment that if you haven't gone into labor by next week, you will need to be admitted to the hospital so labor can be induced. Emotionally, you're relieved to have an end to the waiting in sight, but you wonder whether inducing labor is necessary and if it is safe.

Because no one really understands how normal labor starts, we are at a loss to explain why some labors don't start until weeks after the due date. This would not be of concern, except that after nine months of pregnancy have passed, the placenta often fails to keep up with the growing oxygen and nutritional needs of the overdue baby. In fact, the mortality rate of babies born after 43 weeks is double that of those born on time. After 44 weeks, the mortality rate is triple the normal rate. That is why most practitioners are extremely reluctant to allow pregnancies to continue much past 42 weeks.

Antepartum testing determines which babies are at highest risk for difficulties before and during labor. Most practitioners routinely recommend such testing after 41 weeks. It includes a non-stress test (see Chapter 18) and a biophysical profile (see Chapter 4) performed during an ultrasound exam. If this testing reveals abnormalities, induction of labor is recommended. Even if the test results are normal, induction is recommended at 42 weeks.

How is labor induced? There are a variety of methods, used alone or in combination, which can induce labor. If the cervix is more than slightly dilated, the simplest way is to rupture the membranes artificially (see Chapter 20). Most women will go into labor within 24 hours after the membranes rupture.

There are a number of disadvantages to using this method alone, however. First, not all women will go into labor. Second, as soon as the membranes are ruptured, the potential exists for chorioamnionitis, infection of the membranes and amniotic fluid. This type of infection affects the mother as well as the baby. The risk of infection increases over time. There is not much chance for infection to occur if the labor is well along and the delivery will happen within the next few hours. However, if labor has not even started, the delivery may not take place for 24 hours or more, which significantly raises the possibility of infection. Chorioamnionitis can be treated with antibiotics, but it is far preferable to avoid infection all together, if possible.

The second method of inducing labor is the use of prostaglandin gel. This technique became available only a few years ago, but it has become popular very quickly. Prostaglandin gel contains one type of the hormone prostaglandin, which naturally causes the cervix to soften and thin out in preparation for labor. Prostaglandin gel may even stimulate mild contractions and, for some women, this is enough to start labor.

Prostaglandin gel is applied directly to the cervix during a cervical exam. Because of its potential to cause contractions, it is usually applied in the hospital setting and the baby is monitored for several hours thereafter. If no significant change occurs after four hours, a second dose of gel may be applied.

Prostaglandin gel may stimulate labor alone, but more commonly it is used in conjunction with Pitocin. Pitocin is the synthetic version of the naturally occurring hormone oxytocin, which causes uterine contractions. The advantage of giving prostaglandin gel first is that the cervix tends to become thinner and even slightly dilated after the gel is applied, making the Pitocin more likely to be effective at smaller doses. Pitocin is administered initially in minute quantities, and the amount is gradually increased over 20-minute intervals until contractions begin. The fetus is monitored during administration of Pitocin to make sure that the amount given does not cause the baby stress or contractions that are too frequent. If labor has not started within 12 to 24 hours after application of prostaglandin gel, the mother is readmitted to hospital to receive Pitocin through an intravenous line.

Are there disadvantages to Pitocin? Some practitioners believe that Pitocin causes stronger contractions than those that occur naturally. Most research suggests, however, that Pitocin-induced contractions are very similar to those of normal active labor. The potential does exist to cause contractions that are more frequent than naturally occurring contractions and, therefore, these contractions may be more stressful for the baby. That's why careful monitoring is essential during administration of Pitocin. It is easy to decrease the frequency of contractions just by lowering the dose of Pitocin if there is any indication that the contractions are occurring too close together.

The disadvantages must be weighed against the risks, of course. It would be inappropriate to induce labor just to have the delivery occur on a convenient date. The use of Pitocin for induction is justified only if the baby is at significant risk for serious problems, either because an abnormality has been found on antepartum testing, or because the baby is two weeks overdue or more.

There are other, less common reasons for inducing labor. These include preeclampsia, gestational diabetes (but not before 38 weeks), and intrauterine growth retardation (IUGR) if the fetus is in less than the 10th percentile for gestational age. In the case of pre-eclampsia, induction is performed to treat the mother. In the case of gestational diabetes or IUGR, the fetus is at risk.