Ideally, labor should begin spontaneously in order to best respect the natural physiology of childbirth.

However, when labor is slow to start, induction may be offered. This involves artificially triggering labor using chemical or mechanical means.

It is important to distinguish between labor induction and labor stimulation:

• Induction (or triggering) involves artificially initiating labor using a synthetic hormone, such as oxytocin (Pitocin, Syntocinon), in the absence of effective or regular contractions.
• Stimulation, on the other hand, aims to strengthen contractions that are already present in order to make them more effective—by regularizing them and increasing their intensity—to help labor progress.

In Quebec, as elsewhere in Canada, approximately 24% of deliveries are induced, although this rate varies from one facility to another.

Before proceeding with induction, several factors must be evaluated: the medical justification, the most appropriate method, and the potential risks to the mother and child. The Society of Obstetricians and Gynecologists of Canada emphasizes that any induction must be based on a clear obstetric or medical indication. The most common reason remains prolonged pregnancy.

Several situations may justify induction or stimulation of contractions, including:

• medical complications such as preeclampsia, maternal illness, or hemorrhage;
• post-term pregnancy (nearly 42 weeks), which occurs in about 6% of cases;
• rupture of membranes without spontaneous onset of labor after several hours;
• intrauterine growth restriction in the baby;
• or conditions such as gestational diabetes or poorly controlled hypertension.

These common situations deserve to be addressed in prenatal classes, as they will affect many expectant mothers.

That said, certain factors can influence the decision to induce labor or not. Each case must be evaluated individually, taking into account the risk-benefit ratio.

Factors to consider include:

• a body mass index (BMI) greater than 40;
• maternal age over 35;
• a baby whose weight is estimated to be over 4 kg;
• poorly controlled diabetes;
• or a breech presentation of the baby.

Predictors of success for labor induction

Certain signs can be used to estimate the chances of successful induction. For example, a woman who has already given birth vaginally generally has a better prognosis.

Another reference tool is the Bishop score, which assesses the “maturity” of the cervix, i.e., its readiness for delivery. This score is based on five factors:

• cervical effacement (its length, expressed as a percentage);
• dilatation (in centimeters);
• the consistency of the cervix (soft, medium, or firm);
• the position of the cervix (anterior or posterior);
• the baby’s station, or how far it has descended in relation to the bony landmarks of the pelvis.

The more favorable these conditions are—cervix effaced, dilated, soft, well positioned, and baby engaged—the higher the chances of a successful vaginal delivery following induction.

Finally, current data show that medically justified induction does not increase the risk of cesarean section compared to a wait-and-see approach, contrary to popular belief.

Induction of labor: methods, indications, and success factors

Natural, mechanical, or pharmacological induction

Induction of labor may be considered when labor is slow to start spontaneously or in the presence of certain medical conditions. The methods used can be natural, mechanical, or pharmacological.

Among the natural methods, certain approaches are sometimes suggested to promote the onset of labor, although the scientific data is variable:

• Sexual intercourse, which can stimulate the production of oxytocin and prostaglandins, two elements involved in the induction of labor.
• Nipple stimulation, either manually or with a breast pump, to promote the natural secretion of oxytocin.
• Acupuncture, osteopathy, homeopathy: although evidence of their effectiveness is limited, these approaches can contribute to relaxation or bodily harmonization at the end of pregnancy.
• Castor oil: this natural laxative works by indirectly stimulating the uterus via the smooth muscles of the intestines. Its use must be strictly supervised, only after 39 weeks of pregnancy, in a single dose of 60 ml. Inappropriate use can lead to cramps, diarrhea, and dehydration.
• Membrane stripping: performed by a professional when the cervix is sufficiently effaced and dilated, this procedure promotes local prostaglandin production. It may cause slight bleeding and irregular contractions in the short term.

Mechanical and pharmacological methods

When natural methods are ineffective or not indicated, other options are available:

• Prostaglandin tampon (Cervidil): inserted into the vagina or directly into the cervix, it promotes cervical ripening (effacement and dilation).
• Foley catheter: a catheter with a balloon is inserted into the cervix to exert mechanical pressure, thereby facilitating its gradual opening.
• Oral misoprostol: increasingly used, this medication stimulates uterine contractions. It can be administered in repeated doses according to an established medical protocol.
• Amniotomy: involves artificially rupturing the amniotic sac if the cervix is favorable, in order to initiate or intensify labor.
• Synthetic oxytocin by intravenous injection (Pitocin/Syntocinon): used to initiate or strengthen contractions. It is administered gradually under continuous monitoring, as it can cause more intense contractions than natural labor.

Monitoring and clinical considerations

All of these interventions require close monitoring of fetal and maternal well-being. A fetal monitor is usually installed as soon as oxytocin is administered.

It is important to note that the effectiveness of these methods depends on several factors, including cervical maturity, assessed using the Bishop score, as well as factors such as obstetric history, fetal position, and associated medical conditions.

In some cases, induction may fail. A reassessment will then be carried out, and a decision may be made to try induction again or to perform a cesarean section if necessary.

Here are some other videos related to the topic, again with the aim of increasing your knowledge and better preparing you for the birth of your baby:

• Rupture of the amniotic sac
• Contractions
• Warning signs of impending labor
• Progression of labor

The following articles also provide additional relevant information on the subject:

• The realities of childbirth
• Water breaking
• Soon, I’ll be a dad
• Ah, hormones!
• Cesarean section

Marie Fortier
The baby expert

Updated: April 2025.

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