Labor is the process by which the baby and placenta leave the uterus, or womb. This process normally begins on its own around the 40th week of pregnancy. In some cases, however, medical intervention is needed to start labor.
Your doctor may induce labor by using medications and other methods to bring on contractions. These contractions occur when the muscles of your uterus tighten and then relax. They help push your baby out of the uterus and encourage your cervix to open up for childbirth. The cervix is the opening to the uterus and sits atop the vagina, or birth canal. Your baby comes down through the cervix and into the vagina during delivery.
According to the Centers for Disease Control and Prevention, approximately 23 percent of births in the United States are induced. Your doctor may need to induce labor if you and your baby are at risk for complications.
One common reason for inducing labor is that your baby is overdue. Normal pregnancies last about 40 weeks. When pregnancy lasts longer than 42 weeks, it’s considered a post-term pregnancy. A post-term pregnancy can be dangerous for your baby, as the placenta may not supply sufficient food and oxygen to your baby after 42 weeks.
Other common reasons for inducing labor include the following:
- Your placenta is separating from your uterus.
- You have an infection in your uterus.
- You have high blood pressure.
- Your water breaks, but contractions don’t begin.
- Your baby has a growth problem.
- You have an existing health condition, such as diabetes, that may harm you or your baby.
- You have Rh incompatibility.
Some women wish to induce labor before the 40-week mark for nonmedical reasons. However, most doctors don’t recommend this because the baby may not be fully developed yet. Labor should only be induced to protect the health of you and your baby. Your doctor can use a variety of medications and medical techniques to help induce labor.
Ripening the cervix is often the first step in inducing labor. Cervical ripening involves encouraging the cervix to become softer, thinner, and wider. Normally, your cervix begins to erode and dilate naturally on its own during labor. This allows the baby to leave the uterus and enter the birth canal. However, if your cervix shows no signs of these changes, your doctor will need to take certain steps to ripen the cervix.
Techniques for ripening the cervix include:
- application of prostaglandin medications to the cervix
- gradual dilation of the cervix with an osmotic dilator
- dilation of the cervix with a rubber catheter
The most commonly used method for cervical ripening is the application of a prostaglandin medication. Prostaglandins are naturally occurring hormone-like substances that stimulate certain changes in the cervix that cause it to ripen. The two main prostaglandin drugs used today are dinoprostone and misoprostol.
Dinoprostone is available as Prepidil and Cervidil. Prepidil is a gel that’s rubbed onto the mucous membranes of the cervix with an applicator. Cervidil is a wafer-like insert that’s positioned in the top of the vagina. Once the gel or insert is in place, it slowly releases prostaglandins into the nearby tissues.
Prepidil and Cervidil usually take six to 12 hours to take full effect, after which the cervix is re-evaluated to see if labor can be induced. If your cervix still hasn’t ripened, your doctor may give you another dose of medication.
Dinoprostone has few associated side effects. In rare cases, however, women may experience hyperstimulation of the uterus. This condition causes the uterus to contract too frequently.
Misoprostol (Cytotec) is another prostaglandin drug that’s used as a cervical ripening agent. Your doctor will place it in the upper part of the vagina every three to four hours to help promote labor. The medication may also be taken orally, but it’s believed that the vaginal route is best.
Misoprostol is normally prescribed to treat stomach ulcers. However, the drug has also been shown to be useful in inducing labor. It appears to be as effective and safe as dinoprostone but less expensive. Like dinoprostone, a potential side effect of misoprostol is hyperstimulation of the uterus. However, this occurs in a very small percentage of women.
Gradual dilation of the cervix
Gradual cervical dilators help ripen the cervix by slowly absorbing fluid from the tissues. The most commonly used cervical dilator is Laminaria japonica. This is a dried seaweed stem that can absorb cervical fluid quite quickly over the course of four to six hours.
Though they can be effective in inducing labor, cervical dilators are more likely to trigger an infection in the cervix. As a result, they’re less popular among doctors than prostaglandin medications.
Catheter dilation of the cervix
Catheter dilation of the cervix involves using a Foley catheter. This catheter is a long, narrow tube made of latex that has a balloon tip. During catheter dilation, your doctor guides the Foley catheter through the vagina and into the cervical canal. Then, they inflate the balloon to a diameter of 2 to 3 inches, encouraging the cervix to open.
Catheter dilation can help ripen the cervix, but it’s considered to be an invasive procedure. Doctors only use it in special circumstances or when other methods to induce labor have failed.
Stripping the membranes can expedite the onset of labor when the cervix is only partially dilated. During this procedure, your doctor inserts a gloved finger into your cervix and gently separates the amniotic sac, or membranes, from the uterine wall. The amniotic sac is the fluid that surrounds your baby in the womb. When this fluid is released, it produces hormones that help encourage contractions to start.
Stripping the membranes works poorly in pregnancies less than 38 to 39 weeks along. Additionally, it isn’t a good method to use when an urgent need for delivery arises. It takes about a minute and can be painful for women having their first baby.
Artificial rupture of membranes is also known as amniotomy. During this procedure, your doctor deliberately breaks the amniotic sac. This allows the amniotic fluid to be released. Rupturing the membranes or bag of waters that surround the baby has been used to induce labor for many years.
Doctors routinely perform this procedure once uterine contractions are sufficiently strong and frequent. However, the head of the baby must be against the cervix before the membranes can be ruptured. The umbilical cord also needs to be away from the cervical canal prior to the procedure. Taking these preventive measures helps reduce the risk for infection in the baby.
Oxytocin is a small protein that’s produced by tissues and glands in the brain. This protein is secreted during normal labor, especially near delivery. When labor is delayed, your doctor can administer oxytocin to encourage your uterus to start contracting regularly.
You can get Oxytocin through a vein using a controlled medication pump. The dose needed to cause sufficient contractions varies considerably from one woman to another. In general, however, the goal is to establish three to five uterine contractions every 10 minutes.
The strong, frequent contractions help the cervix to ripen and allow the baby's head to descend. The initial rate of cervical dilation may be fairly slow, and might be even less than 0.5 centimeters per hour. Once the cervix is approximately 4 centimeters dilated, the goal is about 1 centimeter per hour or more. To monitor the strength and frequency of uterine contractions, a pressure catheter may be placed in the vagina. Such catheters are made of thin, flexible plastic and don’t cause any significant discomfort.
Oxytocin rarely causes side effects when it’s used properly. The following are potential side effects:
- Hyperstimulation of the uterus can occur when contractions happen too frequently over an extended period. This can lead to decreased blood flow to the placenta.
- Uterine rupture, or tearing of the uterine wall may happen due to hyperstimulation of the uterus. Although this side effect is rare, it’s more common in women who’ve had previous uterine surgery or cesarean deliveries.
- Water retention, electrolyte imbalance, and water intoxication can occur as a result of high doses of oxytocin.
Your doctor may recommend inducing labor if your pregnancy lasts longer than 42 weeks or if you have a medical problem that could harm you or your baby. Inducing labor is often the best way to keep you and your baby healthy. However, inducing labor early for nonmedical reasons can be harmful, so it’s best to let labor begin on its own.
It’s recommended to wait until at least the 39th week of pregnancy to induce labor. This gives your baby the time they need to fully grow and develop before they’re born.