Induction of labor: Clinical sciences

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Introduction0:00–0:31

Induction of labor is the initiation of parturition through the use of medications and other processes that mimic normal labor.
This procedure can be done when the benefits of delivery outweigh the risks of continuing a pregnancy. Depending on the patient’s initial cervical exam, you may need to ripen the cervix or stimulate contractions with a variety of methods.
Ultimately the goal of labor induction is to have a spontaneous vaginal delivery. Okay, when a pregnant patient presents for induction of labor, you should assess if there are any contraindications present before doing anything.

Assess for contraindications0:31–2:54

Contraindications are conditions that prevent a safe vaginal delivery, such as transverse fetal lie, non-reassuring fetal status, or umbilical cord prolapse.Here’s a clinical pearl!
An umbilical cord prolapse occurs when the umbilical cord falls below the presenting part of the fetus, usually through a dilated cervix into the vagina.
This is an obstetric emergency that needs immediate C-section delivery!Additional contraindications include patients with previous disruption of the myometrium, including a prior classical c-section with a uterine incision, a prior myomectomy entering the uterine cavity, or a prior uterine rupture.
These patients are at a high risk of uterine rupture during labor, which makes induction inadvisable. Additionally, some patients may have abnormal placentation, such as a placenta previa, where the placenta covers the cervical os and bleeds profusely if cervical dilation occurs; as well as abnormal vascular presentation like vasa previa, where the umbilical vessels are unprotected and found in the membranes that cover the cervical os.
Others may have conditions such as invasive cervical cancer, which can block the cervical os and obstruct the ability of a fetus to pass through the birth canal, while also increasing the risk of severe maternal hemorrhage.
Another contraindication is an active viral disease that can be passed to the fetus during delivery. This includes an HIV viral load of more than 1000 in the third trimester; or an active herpes simplex virus infection, specifically, if HSV lesions are present in the genitourinary tract or if a patient experiences prodromal symptoms like genital burning or pain.
Finally, do not induce patients with a gestational age less than 39 weeks, unless they have a medical indication for delivery, like preeclampsia.
Elective induction can be performed at 39 weeks if gestational age has been confirmed. Here’s a clinical pearl to keep in mind!
Fetal morbidity increases starting at 41 weeks, so induction of labor should be revisited with patients who haven’t yet delivered by that time, and induction of labor is definitely recommended if spontaneous labor has not begun by 42 weeks due to the increased risk of stillbirth.

Induction of labor2:54–4:07

Okay, if a contraindication is present, do not proceed with induction of labor. Instead, consider c-section delivery or in cases of fetal malpresentation, an external cephalic version may be attempted.
On the other hand, if contraindications are absent you can proceed with an induction of labor. Your first step is to perform a cervical exam and calculate the Bishop score.
Let’s look at how to proceed once we calculate the Bishop score. This is a scoring system based on a set of criteria noted on the vaginal exam that predicts the likelihood of successful induction of labor.
The Bishop score is helpful in deciding how to start an induction. There are five criteria to consider: cervical dilation, which describes how many centimeters open the cervix is; the position of the cervix within the vaginal canal; the effacement of the cervix indicating how thin the cervix is; the station of the fetal head within the pelvis; and the consistency of the cervix, which softens as labor begins.
Each one is given from 0 to 3 points, and the total value is known as the Bishop score. Of note, cervical dilation is considered the most important of the five scoring elements.

Bishop score < 64:07–10:05

Let’s first look at an unfavorable Bishop score. If the Bishop score is 6 or less, the cervix is considered unfavorable.
This means you will need to perform cervical ripening before the induction process. In normal parturition, the cervix will soften, thin, dilate, and move anteriorly.
Cervical ripening facilitates that process, which increases the likelihood of a successful induction of labor. This can be done with pharmacological agents or mechanical methods of cervical ripening.
The most commonly used ripening agent is a synthetic prostaglandin E1 analogue called misoprostol. It can be administered either by mouth, buccally, or inserted into the vagina.
In addition to ripening the cervix, misoprostol will stimulate uterine contractions. There is also a prostaglandin E2 analogue available called dinoprostone, which works similarly.
Dinoprostone is available in a vaginal form only. Here’s a clinical pearl!
Even though prostaglandins increase the likelihood of vaginal delivery within 24 hours, they actually don’t reduce the rate of C-section delivery, and there’s an increased risk of uterine tachysystole.
This is defined as more than five contractions in 10 minutes. If sustained, this can cause fetal distress and you may need to administer a tocolytic, like terbutaline, to relax the uterine muscle.
Also, keep in mind that all prostaglandins are contraindicated in patients who had a prior c-section but who otherwise qualify for a trial of labor after C-section, as prostaglandin use raises the risk of rupture.
In addition to ripening medications, you can also use mechanical methods to dilate the cervix. This can be done in tandem with, instead of, or after the administration of synthetic prostaglandins.
After completion, the cervix will be dilated anywhere between 3 to 5 centimeters. There are two main devices available: a Foley catheter and a double balloon device.
Foley catheters are inserted through the cervical os and inflated with 30 to 80 milliliters of sterile water. Next, the inflated balloon is retracted against the internal os, causing direct pressure.
The double balloon device is inserted in a similar way to the Foley catheter, but it works differently. There are two balloons that are inflated, which will be placed just above and below the internal cervical os.
The steady pressure on the cervix also causes a release of endogenous prostaglandins which further ripens the cervix. Here are a few clinical pearls!
Membrane stripping is another method to induce labor. It’s performed by using a sterile finger to sweep and separate the chorioamniotic membrane from the wall of the cervix and lower uterine segment.
This increases the local release of phospholipase A2 and prostaglandin F2⍺ and has been shown to increase the likelihood of spontaneous labor within 48 hours.
There’s another type of mechanical cervical dilator available called an osmotic dilator. It’s made of a sterilized natural material like seaweed or synthetic material, which is dehydrated and placed in the cervical os.
Over time, it slowly expands and dilates the cervix as it absorbs local tissue fluid. Osmotic dilators have fallen out of favor for term labor induction in most centers due to increased risk of infection, but they’re still routinely used and safe for cervical ripening prior to dilation and evacuation procedures.Now back to our cervical ripening.
Once you have started to ripen the cervix, you should continually assess the patient’s response. Remember, you have two patients here: mom and baby.
The mother will be connected to an electronic fetal heart rate monitor to continuously assess fetal status. If the fetal status remains reassuring, you should perform a pelvic exam every 3 to 6 hours to assess the responsiveness of cervical ripening.
An adequate response will show the cervix is softening, thinning, and dilating. If using mechanical devices, you’ll note an adequate response when the mechanical devices are no longer in the cervix, which is usually within 8 to 12 hours for Foleys and balloons.Okay let’s talk about what to do if the response is adequate.
Your next step is to administer oxytocin, which activates uterine contractions to simulate spontaneous labor. You can also consider amniotomy at this time, which is the artificial rupture of membranes.
Keep in mind that amniotomy commits the patient to proceed; so this should be part of shared decision-making if there’s no obstetrical or medical indication for delivery and the patient is still in the latent phase.If the initial response to cervical ripening is inadequate, meaning slight cervical change with minimal uterine activity, you can continue with cervical ripening.
This may include a repeat dose of a pharmacological ripening agent at recommended intervals until the maximum cumulative dose is reached or insertion of a mechanical dilator if not previously used.
Continue to reassess the patient’s response. Some patients may have a prolonged inadequate response to cervical ripening, in which case you should re-evaluate the reason for attempting the induction.
If delivery is not medically indicated, you can consider discharging the patient if the fetal status is reassuring and the amniotic sac is intact.
On the flip side, if delivery is medically indicated, you should proceed with a c-section.Here’s a clinical pearl! Before performing an amniotomy confirm the patient's group B strep, or GBS, status.
Positive patients should receive IV antibiotic prophylaxis prior to amniotomy. Currently, there’s insufficient data to guide the timing of amniotomy after the patient has started antibiotics, but a good rule of thumb is to wait 4 hours from the first dose or after the patient has started their second dose.
Now that we have discussed patients with an unfavorable cervix, let’s go back to our Bishop score and talk about patients with a favorable one.

Bishop score > 610:05–10:48

If the Bishop score is above 6, you should directly proceed with oxytocin for induction of labor. This is because the cervix doesn’t need softening or thinning and is already a bit dilated.
Oxytocin will stimulate uterine contractions to mimic spontaneous labor. You may consider an amniotomy at this time as well.
Here’s a clinical pearl! Nipple stimulation is another inexpensive way to induce labor.
In patients with a favorable cervix, nipple stimulation is shown to decrease the number of patients not in labor after 72 hours.Alright, as a quick recap… Induction of labor is the artificial initiation of the labor process.

Review10:48–11:15

First, you should always assess contraindications to induction. Then, use the Bishop score to guide how to start the induction.
Patients with an unfavorable cervix should undergo cervical ripening with pharmacological or mechanical cervical ripening methods, or both.
Patients with a favorable cervix can immediately proceed with oxytocin and possibly amniotomy. Remember that the goal is to have