Induction of labour


Induction of labor is artificial initiation of labor by medical or mechanical means before it begins naturally. The decision to induce labor is typically based on the balance between maternal and fetal risks of continuing pregnancy versus the benefits of delivery. 

Indications for labor induction can be categorized into maternal, fetal, and maternal-fetal conditions.

Maternal Indications for Induction of Labor

  1. Post-term Pregnancy:

    • Defined as a pregnancy that has reached or exceeded 42 weeks of gestation.
    • The risk of complications such as stillbirth, oligohydramnios, and macrosomia increases after 41-42 weeks.

  2. Pre-eclampsia/Eclampsia:

    • Pre-eclampsia (hypertension with proteinuria or signs of organ dysfunction) or eclampsia (pre-eclampsia with seizures) may necessitate induction to avoid further maternal or fetal complications.
    • Delivery is indicated, particularly when severe pre-eclampsia develops after 37 weeks.

  3. Gestational Hypertension:

    • Induction is considered if blood pressure cannot be controlled or if there is a risk of pre-eclampsia.

  4. Premature Rupture of Membranes (PROM):

    • Term PROM (rupture of membranes before labor after 37 weeks) typically leads to labor induction if spontaneous labor does not occur within 24 hours to reduce the risk of infection (e.g., chorioamnionitis).
    • Preterm PROM (before 37 weeks) may require induction depending on gestational age, infection risk, and fetal lung maturity.

  5. Maternal Medical Conditions:

    • Diabetes mellitus: Induction may be indicated in women with gestational or pre-existing diabetes, especially if there are concerns about fetal macrosomia, poor glucose control, or the risk of worsening maternal complications.
    • Chronic Hypertension: Induction may be necessary to prevent maternal complications such as pre-eclampsia or placental abruption.
    • Renal disease, cardiac disease, or other significant maternal comorbidities may also prompt induction if the risks of continuing the pregnancy outweigh the benefits.

  6. Chorioamnionitis:

    • Infection of the amniotic fluid and membranes requires prompt delivery to avoid maternal sepsis and fetal infection.

  7. Intrauterine Fetal Demise (IUFD):

    • If fetal death occurs, labor induction is typically initiated to prevent complications such as coagulopathy.

Fetal Indications for Induction of Labor

  1. Fetal Growth Restriction (FGR/IUGR):

    • Induction may be indicated when the fetus is not growing appropriately (usually below the 10th percentile for gestational age), particularly if there is evidence of placental insufficiency, abnormal Doppler studies, or other signs of fetal compromise.

  2. Oligohydramnios:

    • Reduced amniotic fluid volume can be an indication for induction, especially in term pregnancies, as it is associated with placental insufficiency and poor fetal outcomes.

  3. Fetal Distress:

    • If there are signs of fetal distress, such as abnormal fetal heart rate patterns or biophysical profile abnormalities, induction may be considered to expedite delivery and avoid further compromise.

  4. Non-Reassuring Fetal Testing:

    • Abnormalities on antenatal tests like a non-stress test (NST), biophysical profile (BPP), or Doppler studies may indicate placental insufficiency or impending fetal distress, necessitating induction.

  5. Isoimmunization (Rh Incompatibility):

    • In cases of Rh incompatibility with signs of fetal anemia or hydrops fetalis, induction may be necessary to prevent severe fetal complications.

Maternal-Fetal Indications for Induction of Labor

  1. Multiple Gestations:

    • Induction may be indicated if the pregnancy has reached full term, or if there are complications such as pre-eclampsia, fetal growth restriction of one or more fetuses, or twin-to-twin transfusion syndrome.

  2. Placental Abruption (partial):

    • Induction may be necessary in the case of a partial placental abruption, where the placenta prematurely separates from the uterine wall, leading to fetal compromise and maternal bleeding.

  3. Placenta Previa (if resolved):

    • If a previously diagnosed placenta previa resolves but there are concerns about maternal bleeding or fetal well-being, induction may be considered.

Elective Induction of Labor

  1. Elective Induction at Term:
    • Some inductions are performed for non-medical reasons, typically after 39 weeks of gestation to avoid post-term complications or to accommodate maternal preferences.
    • Elective induction should only be considered when the cervix is favorable (Bishop score ≥6) and the pregnancy has reached full term (≥39 weeks) to reduce the risk of cesarean delivery.

Contraindications for Induction of Labor

Induction of labor is contraindicated in certain situations where vaginal delivery would pose risks to the mother or fetus. These include:

  • Placenta previa: Placenta covering the cervical os, which increases the risk of hemorrhage.
  • Vasa previa: Presence of fetal blood vessels in the membranes that traverse the lower uterine segment.
  • Transverse lie: Abnormal fetal position that makes vaginal delivery impossible.
  • Active genital herpes: Risk of neonatal herpes transmission during vaginal delivery.
  • Previous classical cesarean section or uterine surgery: Risk of uterine rupture during labor.

Methods of Labor Induction

  • Mechanical Methods:

    • Amniotomy: Artificial rupture of membranes to stimulate labor.
    • Cervical ripening agents: Balloon catheters or dilators to soften the cervix.

  • Pharmacologic Methods:

    • Oxytocin (Pitocin): Used to stimulate uterine contractions.
    • Prostaglandins (e.g., misoprostol, dinoprostone): For cervical ripening and induction.

  • Membrane Sweeping: A procedure to stimulate labor by separating the amniotic membranes from the lower uterine segment during a cervical exam.

 

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