Inducing Labor - Indications and Contraindications

Introduction

Inducing labor or labor induction is an obstetric procedure performed to stimulate the onset of labor. Induction of labor depends on the status of the cervix, the mother’s health, the baby’s health, gestational age, weight, size, and the position of the baby in the uterus. Induction of labor is performed in various clinical conditions, including the rupture of the amniotic membrane and post-term pregnancy. Various induction methods are available, and the choice of method depends on the national guidelines, the individual’s clinical factors, and the protocol.

What Does Inducing Labor Mean?

Inducing labor refers to the process of stimulating labor through pharmacological or non-pharmacological methods. The uterus has the body and the cervix. The body of the uterus is composed of smooth muscles, and the cervix is composed of collagen. The cervix undergoes various changes during pregnancy and labor. Mechanical and pharmacological methods of induction can help induce physiological changes in the cervix, such as thinning, shortening, and dilating.

What Are the Indications for Inducing Labor?

Labor induction is indicated for early-term (37 to 38 weeks), late preterm (34 to 36 weeks), late-term (41 weeks), and post-term (beyond 42 weeks) pregnancy. It depends on the patient’s obstetric and medical history. It is performed when it is determined that the outcomes for the mother and the fetus are better with induction methods than waiting for the onset of spontaneous labor. The indications for labor induction include the following:

• Oligohydramnios (reduced amniotic fluid volume) between 36 to 37 weeks of gestation.

• Post-term pregnancy, that is, if the pregnancy has gone beyond the end of 42 weeks.

• Intrauterine fetal growth restriction, with no abnormalities in the Doppler study (a test that uses high-frequency sound waves to determine the blood flow through the blood vessels), between 38 to 39 weeks of gestation.

• Intrauterine fetal growth restriction, with the absent end-diastolic flow at 34 weeks of gestation.

• Intrauterine fetal growth restriction, with reversed end-diastolic flow at 32 weeks of gestation.

• Chronic hypertension and not under medications, between 38 to 39 weeks of gestation.

• Gestational hypertension at 37 weeks of gestation.

• Preeclampsia (a condition with high blood pressure, fluid retention, and proteinuria)

• With severe characteristics at 34 weeks of gestation.

• Well-controlled pre-gestational diabetes diet or exercise-controlled gestational diabetes at 34 weeks of gestation.

• Abruptio placentae (detachment of the placenta from the womb).

• Chorioamnionitis (swelling of the membranes and chorion of the placenta).

• Intrauterine fetal demise.

What Are the Contraindications for Inducing Labor?

Contraindications for inducing labor depend on the following factors:

• Placenta previa or vasa previa (a condition in which the placenta blocks the neck of the uterus and interferes with the delivery of the baby).

• Transverse fetal presentation.

• Umbilical cord prolapse.

• History of prior cesarean section.

• Active herpes infection.

• History of prior myomectomy breaching the endometrium.

What Are the Methods of Inducing Labor?

Labor induction is performed with pharmacological and non-pharmacological methods of induction. It includes the following:

Pharmacological Methods:

• Prostaglandins - The prostaglandin hormones are produced naturally in the body at the time of onset of labor. Synthetically manufactured prostaglandins are used to ripen the cervix and induce contractions. It acts on collagen in the cervix, promotes ripening, and stimulates the onset of labor. Prostaglandin preparations are available as gels, suppositories, lactose-based vaginal tablets, and pessaries or inserts for vaginal and intracervical administration. It is also available for endocervical or extra-amniotic, intravenous, and oral administration.

• Misoprostol - An effective uterine contraction can be stimulated with Misoprostol, a prostaglandin analog. It is available as oral, vaginal, rectal, and buccal or sublingual tablets. Oral Misoprostol has a rapid onset of action, but vaginal administration has a more prolonged action. It is widely used in other cases of pregnancy, such as the termination of pregnancy.

• Oxytocin - The oxytocin hormone is produced naturally in the body, and it induces uterine contractions during the second and third stages of labor. Oxytocin is a common induction agent that is intravenously administered. It is administered when the cervix is dilated, and it is combined with artificial rupture of the amniotic membranes in some cases. It can cause excess contractions if the doses are not titrated accurately.

• Nitric Oxide Donors - Nitric oxide helps in cervical ripening. Nitric oxide donors such as isosorbide mononitrate, sodium nitroprusside, and nitroglycerin are used to promote cervical ripening. Nitric oxide is also administered as a vaginal tablet to induce labor.

• Mifepristone - It is a progesterone antagonist that was previously used in combination with prostaglandins in the first and early second trimester of pregnancy terminations. It induces uterine contractions and is available as an oral tablet.

Estrogens, relaxin, corticosteroids, and hyaluronidase, were thought to encourage cervical ripening. However, these preparations are not common in current practice.

Non-Pharmacological Methods:

• Catheters - Foley urinary catheters are used for inducing labor. Double-balloon and cook catheters are specifically used for inducing labor. The catheter is inserted to reach the extra-amniotic space, and then the balloon is inflated to position the catheter in place and is left until they are expelled. The inflated catheter stimulates uterine contractions.

• Laminaria Tents - Sterile seaweed or synthetic materials are used to manufacture laminaria tents. These devices are inserted into the cervical canal and expanded to gradually stretch the cervix and induce contractions.

• Membrane Sweep - Membrane sweeping or stripping has been carried out for many years to induce labor. The doctor detaches the membrane from the lower uterine segment by moving the examining finger circularly. This process increases the production of prostaglandins and induces labor.

• Amniotomy - The amniotic membranes usually rupture spontaneously during labor. It ruptures when the cervix dilates and stretches in preparation for childbirth. Amniotomy is a procedure in which the membrane is ruptured using a plastic hook or surgical forceps to induce labor.

• Breast Stimulation - Previously, breast stimulation was used to stimulate uterine contractions, as it triggers the release of oxytocin.

Other Methods:

• Castor Oil: The laxative properties of castor oil stimulates intestines and bowels, which further induces uterine contractions.

• Acupuncture: The insertion of fine needles at specific points in the body stimulates uterine contractions.

• Homeopathy: The use of some homeopathic preparations is thought to induce uterine contractions.

What Are the Complications of Inducing Labor?

Induction of labor involves the following complications:

• Low fetal heart rate.

• Uterine rupture.

• Infections.

• Bleeding after delivery.

Conclusion

Induction of labor is a widely accepted practice in obstetric interventions. Several methods of induction are available, and the choice of the method depends on the clinical condition of the mother and the fetus. It is performed for better management of labor in certain clinical conditions rather than waiting for the spontaneous onset of labor, which might cause complications.