Management of Labor Health Article

Stripping of Membranes

Stripping the membranes may be appropriate to expedite the onset of labor when the cervix is only partially dilated, at least 1 cm in diameter. This procedure is performed by the doctor inserting a finger into the cervix and sweeping it around the lower portion of the uterus between the fetal membranes and the uterine wall, in an attempt to strip the membranes away from their loose attachment to the uterine wall. This procedure works very poorly in pregnancies less than 38 to 39 weeks along, and is not a good method to use when an urgent or semi-urgent need for delivery arises. It can be somewhat painful for women having their first baby, though the procedure only takes about one minute. When performed, membrane stripping can increase the likelihood of entering spontaneous labor in the next several days.

Management of Labor Induction

Given the importance of the cervical status in determining the success or failure of induced labor, it is not surprising that various treatments have been developed to improve the cervical status prior to labor induction. Ripening the cervix is often the first step. Currently used methods of ripening the cervix include:

• Application of prostaglandin medications to the cervix;
• Gradual dilation of the cervix with an osmotic dilator; and
• Dilation and stimulation of biochemical changes in the cervix with a rubber catheter.

Prostaglandin Drugs

The most commonly used method for cervical ripening is the application of a prostaglandin agent. Prostaglandins are naturally occurring hormone biochemicals that stimulate changes in the cervix to ripen it. There are two main prostaglandin drugs commonly in use today: dinoprostone and misoprostol.

Dinoprostone

This drug comes in two forms: Prepidil and Cervidil. Prepidil is a prostaglandin gel that is placed into the mucous membranes of the cervix with an applicator. Cervidil is a wafer-like insert that is placed in the top of the vagina where it slowly releases the prostaglandin into the nearby tissues, including the cervix. Both of these products contain the prostaglandin dinoprostone, but in different amounts and release times. These products usually take 6 to 12 hours to take effect, after which the cervix is re-evaluated to see if labor can be induced. If the status of the cervix is still unfavorable, a second application may be placed after the first is removed (usually the following day). The side effects of this drug are few, but it may throw a small number of women into progressive labor, which is actually a desirable side effect. Also, a very small percentage of women treated with these medications may experience hyperstimulation of the uterus, causing the uterus to contract too frequently.

Misoprostol

Misoprostol (Cytotec) is another prostaglandin drug serving as a cervical ripening agent. Misoprostol is normally given in 100 microgram tablets for stomach ulcers. Numerous medical studies of this drug for labor induction have been performed, and it appears to be as effective and safe as dinoprostone, but less expensive. Different dosing protocols have been studied for labor induction, but the most experienced authorities recommend 25 micrograms (one-fourth of a 100 microgram tablet) placed in the upper vagina every 3 to 4 hours. Because there is little experience using misoprostol for the induction of labor in women who have had a previous cesarean section, most physicians would not use misoprostol in this setting. As with the dinoprostone, frequent uterine contractions (hyperstimulation of the uterus) may occur in a very small percentage of women treated with misoprostol in a dose of 25 micrograms every 3 to 4 hours. Unlike dinoprostone, misoprostol can be taken orally, though most experts feel that the vaginal route of administration is best for labor induction.

Gradual Dilation of the Cervix

Gradual cervical dilators that work by slowly absorbing fluid from the tissues are sometimes used to ripen the cervix, though, they are much less popular among physicians than the prostaglandin agents discussed above. The most commonly used of these dilators is Laminaria japonicum, a dried seaweed stem that absorbs fluid quite readily over approximately 4 to 6 hours. Dilating the cervix gradually has the advantage of not causing the uterus to contract very much, if at all. There is a greater chance that this procedure could introduce an infection into the cervix than using the prostaglandin agents.

Catheter Dilatation of the Cervix

During catheter dilation, the Foley catheter, which is made of latex and has a balloon tip, is placed into the cervical canal and the balloon is inflated to a diameter of about 2 or 3 inches. This procedure dilates the upper cervical canal but also strips the membranes away from the lower portion of the uterus. Some practitioners who use this method also fill the catheter with saline to encourage the membranes to separate from the lower uterus. The main disadvantage of this method is its invasive nature, since the catheter actually breeches the natural mucus barrier of the cervical canal and lower uterus. This method is generally reserved for special circumstances or when other methods have failed.

Amniotomy (Artificial Rupture of Membranes)

Rupturing the membranes or bag of waters that surround the fetus has been used to augment or induce labor for many years. Obstetricians routinely perform this procedure, known as amniotomy, once uterine contractions are sufficiently strong and frequent. However, the head of the fetus must be against the cervix and the umbilical cord away from the cervical canal before the membranes can be ruptured. Amniotomy before the active phase of labor is associated with a higher rate of infection in the fetus and fetal membranes. Amniotomy performed in the active phase of labor can shorten the time to delivery.

Oxytocin (Pitocin)

Oxytocin is a small protein that is made by human brain tissues and the pituitary gland. It is secreted during normal labor, especially near delivery. Its role in the onset of natural labor or in the active phase of labor is uncertain. Nonetheless, oxytocin clearly causes the uterus to contract and has been used for decades in obstetrics. Although some women state that labor augmented or induced with oxytocin is more painful or difficult than spontaneous labor, there is no medical reason to believe that contractions induced by oxytocin are different from spontaneous labor. Induced labor, however, frequently lasts longer than spontaneous labor because there is no gradual preparation of the cervix as might occur in natural labor.

Administration

Oxytocin is administered intravenously using a controlled medication pump to initiate and maintain regular contractions of the uterus. The dose necessary to cause sufficient contractions varies considerably from woman to woman. In general terms, the goal of oxytocin administration to augment or induce labor is to establish three to five uterine contractions of a moderate-to-strong nature every 10 minutes to ripen the cervix and allow the baby's head to descend. The initial rate of cervical dilation may be fairly slow, even less than 0.5 cm per hour. Once the cervix is completely effaced and approximately 4 cm dilated, the goal is about 1 cm per hour or more.

Different experts have developed different dosage protocols for oxytocin use. These protocols have not been compared regarding safety and comfort, but it is unlikely that the differences between them are clinically important. In general, it is reasonable to start the oxytocin infusion at about 0.5 to 2.0 milliunits of oxytocin per minute and increase it 1 to 2 milliunits of oxytocin per minute every 20 to 40 minutes. The eventual maximum dose of oxytocin required during an induction of labor varies considerably from patient to patient. Only a small percentage of patients require more than 20 milliunits of oxytocin per minute and very few require more than 30 milliunits of oxytocin per minute. Dosages may vary. Your doctor will prescribe what is right for you.

Augmentation or induction of labor for attempted vaginal delivery after a prior low transverse cesarean section is slightly controversial. Women with prior classic cesarean sections are not candidates for low transverse cesarean sections, augmentation, or induction. High-dose oxytocin protocols should not be used for women with prior pregnancies, especially with prior cesarean sections, attempting vaginal birth.

Some physicians feel that women undergoing augmentation of labor with oxytocin should have a pressure catheter placed in the uterus to monitor the strength and frequency of the uterine contractions. Such catheters are made of thin, flexible plastic and are placed by vaginal examination.

Side Effects

Serious side effects (although rare with proper oxytocin use) include the following:

• Hyperstimulation of the uterus, causing too frequent or prolonged contractions, is the most common, worrisome side effect. It can lead to decreased blood flow to the placenta. If hyperstimulation occurs, the physician should either decrease the infusion rate of oxytocin or completely stop it, depending upon the clinical circumstances. In severe cases, medication can be given to quickly relax the uterus.
• The uterus may rupture due to hyperstimulation and, although rare, it is more common in women who have had previous uterine surgery or low transverse cesarean sections.
• High doses can cause water retention, electrolyte imbalance, and water intoxication.

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