Induction of Labor Notes

Induction of Labor

Induction of labor is the process of initiating labor artificially. It's akin to jump-starting a car's engine, setting off a chain of events to bring about delivery. The uterus, initially in a quiescent state, is stimulated to start contractions using various methods.

Augmentation of Labor

Augmentation of labor is applied when the uterus is already contracting, but the contractions are deemed inadequate in terms of strength, frequency, or duration. It's like stepping on the accelerator to increase a car's speed—enhancing the existing labor process to achieve a successful delivery.

Induction vs. Spontaneous Labor

Induction of labor stands in contrast to spontaneous labor. Spontaneous labor occurs when the uterus naturally initiates the labor process, without external interventions. Induction of labor, however, relies on external interventions, such as medications or mechanical methods, to trigger contractions.

Indications and Timing for Induction of Labor

There are specific indications that warrant induction of labor, and the timing is crucial to optimize outcomes:

  • PIH (Pregnancy-Induced Hypertension):

    • Mild preeclampsia: Induce labor at 37 weeks of pregnancy to mitigate risks associated with prolonged hypertension.

    • Severe preeclampsia: Induce labor at 34 weeks of pregnancy, balancing fetal maturity with maternal well-being.

    • Eclampsia or HELLP syndrome: Initiate labor immediately upon diagnosis to prevent further complications.

  • Premature Rupture of Membranes (PROM):

    • PROM (after 37 weeks): Induce labor immediately to reduce the risk of infection and other complications.

    • Preterm PROM (before 37 weeks): Induce labor at 34 weeks, depending on fetal lung maturity studies.

  • Post-term Pregnancy: Induce labor immediately when pregnancy is ≥\ge 42 weeks to avoid risks associated with placental insufficiency.

  • Abruptio Placenta: Immediate delivery and induction of labor to control bleeding and ensure maternal and fetal safety.

  • Chorioamnionitis: Immediate induction of labor upon diagnosis to combat infection and prevent sepsis.

  • Oligohydramnios: Induction of labor at 36 weeks; if associated with IUGR (Intrauterine Growth Restriction), induce at 34 weeks to optimize fetal outcomes.

  • Gestational Diabetes: Induction of labor at ≥\ge 39 weeks to reduce the risk of macrosomia and shoulder dystocia.

  • Rh Isoimmunization:

    • Severe anemia (peak systolic velocity of middle cerebral artery > 1.5 MoM): Terminate pregnancy at 34 weeks to prevent hydrops fetalis.

    • Indirect Coombs test positive, critical titer {note:Higher doses are used for PPH prevention (600 mcg) and treatment (800 mcg).)

    • PGE2 (Dinoprostone): Available as Cerviprim gel (0.5 mg) given intra-cervically. Repeat after 6 hours, maximum 4 doses. Also available as Servidel (10 mg Dinoprostone) in a slow-release formulation, placed in the posterior vaginal fornix for 12 hours.

  • Antiprogesterone drug (Mifepristone or RU-486): 200 mg vaginally.

  • Oxytocin: Can be used for both induction and augmentation of labor. Administered intravenously, starting at a low dose and gradually increasing until adequate contractions are achieved. Monitor fetal heart rate and uterine contractions closely to prevent complications.

Mechanical Methods for Induction of Labor

  • Foley's Induction: A Foley's catheter is inserted into the uterus, its bulb inflated with 30-50 ml of normal saline, and then pulled down to the level of the internal os. This applies pressure to the cervix, promoting dilation and the release of prostaglandins.

  • Stripping of Membranes: This OPD method involves sweeping fingers during a per vaginal examination to stretch the membranes and release prostaglandins. It can be uncomfortable and carries a risk of infection or bleeding.

  • Hygroscopic Dilators: These are better used for abortions; not generally for induction of labor. They work by absorbing fluid and expanding, gradually dilating the cervix.

Contraindications for Induction of Labor

Situations where vaginal delivery is contraindicated also preclude induction of labor:

  • Severe Cephalopelvic Disproportion (CPD): The fetal head is too large to pass through the maternal pelvis.

  • Contracted pelvis: The maternal pelvis is abnormally small or misshapen.

  • Transverse lie: The fetus is lying sideways in the uterus.

  • Brow presentation (mento-posterior): The fetal head is partially extended, making vaginal delivery difficult.

  • Fetal distress or non-reassuring fetal heart rate: Signs of fetal compromise necessitate immediate delivery.

  • Placenta previa: The placenta is covering the cervix.

  • Classical Cesarean Section (previous): A previous vertical incision in the uterus increases the risk of uterine rupture.

  • Previous three LSCS: Multiple prior Cesarean sections increase the risk of complications during vaginal delivery.

  • Previous hysterectomy scar or previous myomectomy scar: These scars may weaken the uterus, increasing the risk of rupture.

  • Active genital herpes infection: Vaginal delivery can transmit the virus to the baby.

Drugs for Augmenting Labor

  • Oxytocin: Administered intravenously to increase the strength and frequency of uterine contractions.

  • Artificial Rupture of Membranes (AROM) or Amniotomy: Deliberate rupture of the amniotic sac to augment labor.

Artificial Rupture of Membranes (AROM)

AROM involves deliberately rupturing the membranes with an instrument such as Kocher's forceps. Kocher's forceps has one tooth on one side and two teeth on the other side, with serrations.

Advantages of AROM

  • Releases prostaglandins, increasing uterine contractions.

  • Allows assessment of amniotic fluid color to detect fetal distress (e.g., meconium staining).

  • Can help decrease bleeding in abruptio placenta by initiating contractions and compressing the placental site.

Risks of AROM

  • Cord prolapse (if the head is not fixed): The umbilical cord can slip down and become compressed.

  • Increased risk of infection: Rupturing the membranes increases the chance of infection.

  • Trauma or injury to the fetal head: Rare, but possible if performed improperly.

Contraindications for AROM

  • Free-floating head: The fetal head is not engaged in the pelvis.

  • HIV-positive mother: Increased risk of vertical transmission of HIV.

  • Active genital herpes infection: Risk of neonatal herpes infection.

  • Intrauterine death of the fetus: No benefit to rupturing membranes.

AROM in Polyhydramnios

In polyhydramnios, AROM can cause sudden decompression of the uterus, leading to placental abruption. In such cases, a controlled rupture of membranes is performed, where a small hole is made in the membrane to allow slow drainage of amniotic fluid. If the membranes rupture suddenly, apply pressure with a sterile pad to control the outflow of amniotic fluid.

Key Scores to Remember in Ob/Gyn

  • Bishop score: Assesses cervical readiness for labor.

  • Biophysical profile: Evaluates fetal well-being using ultrasound and fetal heart rate monitoring.

  • Apgar score: Ass