What are the absolute and relative indications for cesarean delivery?

Indications for Cesarean Delivery

Cesarean delivery indications are divided into absolute indications (where vaginal delivery poses unacceptable maternal or fetal risk) and relative indications (where clinical judgment determines the safest delivery route based on specific circumstances).

Absolute Indications

These conditions mandate cesarean delivery to prevent maternal or fetal mortality:

• Complete placenta previa - the placenta completely covers the internal cervical os 1
• Placenta accreta spectrum - abnormal placental invasion requiring surgical management 2
• Vasa previa - fetal vessels crossing the internal os
• Cord prolapse - umbilical cord presenting before the fetus
• Active genital herpes simplex virus infection with visible lesions at labor onset 3
• HIV infection with viral load >1000 copies/mL 3
• Prior classical or T-shaped uterine incision
• Transverse fetal lie (after 37 weeks when external cephalic version fails or is contraindicated)
• Severe aortic stenosis or aortic dilatation >45 mm (particularly in Marfan syndrome) 4
• Eisenmenger syndrome or severe pulmonary hypertension (mean PAP ≥25 mmHg) - carries 17-33% maternal mortality risk 4

Relative Indications

These require individualized assessment but commonly lead to cesarean delivery:

Fetal Indications

• Nonreassuring fetal status - the single largest contributor (32%) to rising primary cesarean rates 5
• Breech presentation at term - accounts for 18-20% of primary cesareans 6, 7
• Multiple gestation - contributes 16% to increasing cesarean rates, with 3.9 per 1000 live births in twins 5, 1

Labor Abnormalities

• Arrest of dilation - contributes 18% to primary cesarean increases 5
• Prolonged second stage with arrest of descent when estimated fetal weight >4,500 g 2
• Midpelvic arrest with suspected fetal macrosomia 2
• Failed induction of labor - accounts for 4.5% of indications 6

Macrosomia-Related

Labor and vaginal delivery are NOT contraindicated for estimated fetal weights up to 5,000 g in women without diabetes 2. However:

• Prophylactic cesarean may be considered for estimated fetal weight >5,000 g (non-diabetic) or >4,500 g (diabetic) 2
• With estimated fetal weight >4,500 g, prolonged second stage or arrest of descent warrants cesarean 2

Maternal Indications

• Preeclampsia - contributes 10% to cesarean rate increases, though preeclampsia alone typically does NOT mandate cesarean 3, 5
• Aortic dilatation 40-45 mm in Marfan patients 4
• Severe heart failure 4
• Maternal request - accounts for 8% of primary cesarean increases 5

Obstetric Conditions

• Low-lying placenta - trial of labor acceptable if internal os distance is 11-20 mm; cesarean recommended if <11 mm 1
• Prior cesarean with labor abnormalities - though VBAC is not contraindicated by suspected macrosomia 2

Critical Caveats

Suspected fetal macrosomia alone is NOT an indication for induction or cesarean delivery - induction doubles cesarean risk without reducing shoulder dystocia or neonatal morbidity 2. This represents Level B evidence.

Vaginal delivery remains the preferred route for most cardiac patients, with cesarean reserved for obstetric indications or specific cardiac conditions (severe aortic stenosis, aortic dilatation >45 mm, Eisenmenger syndrome, severe heart failure, or oral anticoagulation in preterm labor) 4.

The most subjective indications (nonreassuring fetal status and arrest of dilation) contribute disproportionately to rising cesarean rates compared to objective indications 5, highlighting the importance of strict diagnostic criteria and fetal blood sampling when available.

Regional anesthesia is strongly preferred over general anesthesia for all cesarean deliveries, with general anesthesia reserved for unavoidable situations (postpartum hemorrhage, severe hypoxemia, inability to lie supine, coagulopathy, or patient refusal) 8. The target general anesthesia rate should be <5% 8.