Introduction
Induction of labor is a method of starting contractions in pregnant women who are not in labor to help them achieve vaginal delivery within one or two days. This is done to prevent adverse outcomes for both the mother and the baby. Labor induction is done in conditions like an overdue pregnancy (pregnancy longer than 40 weeks), maternal medical complications, membrane rupture without labor, gestational hypertension, diabetes, and fetal growth restriction. The most common methods used for labor induction include the intravaginal use of misoprostol (pharmaceutical method) and transcervical insertion of the Foley catheter (mechanical method).
What Role Does the Cervix Play in the Induction of Labor?
The cervix is a major functional organ in reproductive physiology. The cervix is a part of the female reproductive system present as a narrow passage at the end of the uterus, connecting the uterus and the vagina. During pregnancy, the cervix remains closed to maintain the pregnancy, and it opens when the pregnant person goes into labor. An unfavorable or unripened cervix is a cervix that is closed and not ready for labor. Inducing labor before making the cervix favorable can lead to prolonged labor and increase the chances of a cesarean section. Therefore, cervical ripening agents are given to prepare the cervix for vaginal delivery and to induce labor.
What Is Intravaginal Misoprostol and How Does It Help in the Induction of Labor?
-
Misoprostol is a chemical compound that resembles natural prostaglandin.
-
Misoprostol has uterotonic (increased tone and contraction of smooth muscles of the uterus) properties similar to prostaglandins.
-
Prostaglandins are natural compounds in the body that help the cervix dilate and contract, facilitating the delivery process.
-
The route of administration of misoprostol can be either intravaginal or oral.
-
Administering Misoprostol vaginally helps the cervix to dilate and smooth muscle fibers to contract, starting the labor process.
-
Misoprostol has many advantages, including its cost-effectiveness, no need for refrigeration, and availability in various dosages and forms.
-
It has side effects like chills, maternal fever, and gastrointestinal symptoms like vomiting, nausea, and diarrhea.
-
To reduce these side effects, misoprostol is given in low doses.
-
The dosage may vary according to the progress of contraction or labor pain.
What Is a Transcervical Foley Catheter, and How Does It Induce Labor?
-
A transcervical Foley catheter is one of the mechanical methods used in labor induction.
-
In this aseptic procedure, a catheter is inserted through the vaginal area using a sterile speculum (an instrument used to dilate the vaginal orifice for examination).
-
A balloon end is present in the Foley catheter, it is inflated with normal saline, and the draining tube is kept closed.
-
The inflation of the balloon end of the Foley catheter exerts pressure on the cervix.
-
This pressure stimulates the release of the hormone called prostaglandins.
-
Prostaglandins are natural hormones present in the body that will help dilate the cervix to begin the labor.
-
Foley catheters induce labor by direct cervix dilatation and stimulating the release of the prostaglandin hormone.
How Does Intravaginal Misoprostol Differ from Transcervical Foley Catheter in Inducing Labor?
-
Intravaginal Misoprostol increases vaginal delivery in patients who are in full term (ready for delivery) with an unripe cervix (cervix not ready for labor). A shorter delivery duration was seen in intravaginal misoprostol than in a transcervical Foley catheter labor induction. This happens because the intravaginal Misoprostol enters the myometrium (smooth muscles of the uterus) directly, causing a greater oxytocic effect on the uterus.
-
An increased dose of Misoprostol can cause hyperstimulation of the uterus, whereas a transcervical Foley catheter reduces the chances of uterine hyperstimulation during labor. Uterine hyperstimulation is a complication of labor induction. In uterine hyperstimulation, a single contraction can last for two minutes or more; in 10 minutes, five or more contractions can also occur. This, in turn, causes damage to the uteroplacental blood flow, resulting in fetal heart rate abnormalities, fetal damage, and fetal hypoxia (lack of oxygen).
-
Pregnant women who underwent cesarean section during their previous delivery are at increased risk of uterine rupture. Uterine rupture happens during labor; as the baby moves through the cervical canal, pressure builds, which can cause uterine tears. Sometimes, it tears along the previous cesarean section scar. Administering Misoprostol can enhance the risk of uterine rupture and is therefore not recommended in such cases.
-
The use of oxytocin to speed up the labor was more seen with a transcervical Foley catheter than intravaginal Misoprostol. Oxytocin is a medication used to stimulate contractions during labor.
-
A transcervical Foley catheter can cause pain, discomfort, and mild bleeding. If it is kept for a prolonged period, there are high chances of infection, especially in cases with premature rupture of membranes.
-
In the intravaginal Misoprostol, a cesarean section was indicated when fetal distress was suspected during the first stage of labor. Cesarean section is indicated in a transcervical Foley catheter in conditions like chorioamnionitis (an intra-amniotic infection) or when the fetal head size does not match the mother's pelvis, which in turn affects the progress of the labor.
-
Chorioamnionitis was much lower in transcervical Foley catheter patients than in pregnant persons who received intravaginal Misoprostol.
-
However, in women with premature rupture of membranes, the chances of chorioamnionitis were higher in transcervical Foley catheter patients than those who received intravaginal Misoprostol.
-
A transcervical Foley catheter is reversible, easily available, and lacks local or systemic side effects than intravaginal Misoprostol.
-
To summarise, even though both intravaginal misoprostol and transcervical Foley catheter have their individual demerits; as induction agents, both intravaginal misoprostol and transcervical Foley catheter have the same effectiveness.
-
The combined intravaginal Misoprostol and transcervical Foley catheter for pregnancy induction have also shown a faster induction time, shorter time to enter active labor and a low cesarean section rate. There was also a decreased risk for tachysystole and meconium. Tachysystole is excessive and frequent uterine contractions leading to an adverse outcome in the fetus. Meconium is an early stool passed by a baby soon after birth. If the baby passes meconium inside the uterus, it might breathe it into its lungs, causing further problems.
Conclusion
The intravaginal use of Misoprostol is a pharmaceutical method of labor induction, and transcervical insertion of the Foley catheter is a mechanical method of labor induction. Both these methods have the same effectiveness in inducing labor. Depending on the pregnant woman's condition, the treating doctor will decide which method of induction is best suited for labor induction in the pregnant person.
