Fetal Compromise During Induction

Fetal compromise during induction is an abnormal fetal heart rate pattern, or other signs of fetal hypoxia, that appear while labour is being induced. It is caused by uterine hyperstimulation, cord compression, placental insufficiency, abruption or an underlying fetal problem that led to induction. It matters because induced contractions are more frequent and stronger than natural ones, so the fetus has less time to recover.

• Risk factors: growth restriction, post term pregnancy, oligohydramnios, previous scar, maternal diabetes, hypertension, high dose misoprostol or oxytocin.
• Pathological patterns need action within minutes.
• Continuous cardiotocography is used for induced labours at risk.

Women have frequent contractions and the fetal heart rate shows late or variable decelerations, tachycardia, bradycardia or reduced variability. Thick meconium may be seen when the membranes rupture.

• Decelerations that follow most contractions.
• Reduced or absent variability for more than 90 minutes.
• Differential diagnosis: fetal sleep, maternal fever, drug effect, cord compression, placental abruption, uterine rupture, maternal hypotension, technical fault.
• Complications: fetal acidosis, hypoxic ischaemic encephalopathy, cerebral palsy, stillbirth, neonatal death, emergency caesarean section, assisted delivery.

The approach is to classify the tracing and to find the cause.

• Cardiotocography: baseline (normal 110 to 160 beats per minute), variability (normal 5 to 25 beats per minute), accelerations, decelerations; pathological features are baseline above 180 or below 100 beats per minute, variability below 5 beats per minute for more than 90 minutes, late decelerations for more than 30 minutes, sinusoidal pattern, or prolonged deceleration beyond 3 minutes.
• Contraction frequency (tachysystole above 5 in 10 minutes) and drug rate or dose.
• Vaginal examination for cord prolapse, bleeding, dilatation and liquor colour; maternal pulse, blood pressure, temperature.
• Fetal scalp lactate where available (below 4.2 mmol/L normal, 4.2 to 4.8 borderline, above 4.8 abnormal).

The principle is to stop the induction agents, resuscitate the fetus in utero and deliver quickly if the tracing does not recover.

• Supportive: stop oxytocin and remove the dinoprostone insert or Foley catheter if needed (wipe misoprostol remnants); left or right lateral position; oxygen 10 L/minute; empty the bladder; two cannulae; call senior help; continuous cardiotocography; prepare theatre.
• Pharmacological: Ringer's lactate 500 to 1000 mL IV over 15 to 30 minutes; terbutaline 0.25 mg subcutaneous once for tachysystole; ephedrine 5 to 10 mg IV for hypotension after epidural; paracetamol 1 g oral for fever above 38 degrees Celsius; ampicillin 2 g IV 6-hourly plus gentamicin 5 mg/kg IV once daily for chorioamnionitis; cefazolin 2 g IV before caesarean section; oxytocin 10 IU IM after birth.
• Procedures: amnioinfusion with sodium chloride 0.9 percent 500 mL over 30 minutes then 3 mL per minute for variable decelerations with oligohydramnios; assisted vaginal delivery when fully dilated with the head low; caesarean section aiming for birth within 30 minutes of the decision for persisting pathological tracing, and within 15 minutes for bradycardia or cord prolapse.
• Special groups: a woman with growth restriction and abnormal Doppler has a lower threshold for caesarean section; a woman with a previous scar needs immediate assessment for scar rupture.
• Red flags: fetal bradycardia, absent variability, scar pain, abruption, thick meconium, maternal collapse.
• Follow-up: umbilical cord blood gas at birth; newborn Apgar score and neurological examination; observation for encephalopathy over 72 hours if depressed; review at 6 weeks.