Failed Augmentation of Labour

Failed augmentation of labour is failure of oxytocin to produce cervical progress in a woman whose spontaneous labour has slowed. It is defined as no change in dilatation after 4 hours of adequate contractions (3 to 5 in 10 minutes, each lasting 40 to 60 seconds) or 6 hours of oxytocin with inadequate contractions, at 6 cm or more dilated.

It results from disproportion, malposition, a poorly responsive uterus, dehydration or exhaustion.

It matters because oxytocin works in weak labour but is harmful when there is obstruction, and the right next step is caesarean section when it fails.

• Risk factors: first pregnancy, obesity, large baby, occiput posterior or transverse position, epidural, advanced maternal age, short stature.
• Oxytocin should not be given when disproportion is clear.
• Adequate contractions must be achieved before declaring failure.

Women have painful contractions with a cervix that does not change despite oxytocin. They are tired, dehydrated and sometimes febrile, with caput and moulding of the fetal head.

• Partograph line crossing the action line on oxytocin.
• Marked caput and moulding of 2 plus or 3 plus.
• Differential diagnosis: cephalopelvic disproportion, malposition, cervical dystocia, hypertonic or incoordinate action, inadequate dose, chorioamnionitis, obstructed labour.
• Complications: prolonged labour, exhaustion, chorioamnionitis, tachysystole, fetal distress, uterine rupture, obstructed labour, caesarean section, postpartum haemorrhage, fistula.

The diagnosis is made on the partograph and by documenting adequacy of contractions.

• Cervical dilatation, station, position, caput and moulding every 2 to 4 hours; membrane status and liquor colour.
• Contraction frequency, duration and strength by palpation or tocography (more than 200 Montevideo units is adequate where intrauterine pressure measurement is available).
• Oxytocin dose reached and duration; cardiotocography.
• Maternal pulse, temperature, urine output and ketones; ultrasound for position and estimated fetal weight.

The principle is to confirm adequate contractions, exclude disproportion and deliver by caesarean section when progress fails.

• Supportive: Ringer's lactate 1 litre IV over 1 to 2 hours; empty the bladder; position changes; one to one support; analgesia (epidural, or pethidine 50 to 100 mg IM 4-hourly); continuous cardiotocography; senior review.
• Pharmacological: oxytocin 10 IU in 1 litre Ringer's lactate (10 mU/mL) started at 12 mL per hour (2 mU/minute) and doubled every 30 minutes to a maximum of 192 mL per hour (32 mU/minute), titrated to 3 to 5 contractions in 10 minutes lasting 40 to 60 seconds, with a cervical examination every 2 to 4 hours; stop oxytocin for tachysystole or fetal distress; benzylpenicillin 5 million units IV then 2.5 million units 4-hourly for group B streptococcus or rupture of 18 hours or more; ampicillin 2 g IV 6-hourly plus gentamicin 5 mg/kg IV once daily for chorioamnionitis, with metronidazole 500 mg IV 8-hourly added after caesarean section; cefazolin 2 g IV before caesarean section; oxytocin 10 IU IM after birth, then 20 IU in 1 litre at 125 mL per hour for 4 hours.
• Procedures: amniotomy when the head is engaged and membranes are intact; manual rotation of a malpositioned head when fully dilated; caesarean section for no cervical change after 4 hours of adequate contractions or 6 hours of oxytocin, for disproportion, or for fetal compromise.
• Special groups: a uterine scar or grand multiparity uses oxytocin only with senior review, lower ceiling rates and continuous monitoring because of uterine rupture; chorioamnionitis needs delivery whatever the dilatation.
• Red flags: tachysystole, abnormal fetal heart rate, fever above 38 degrees Celsius, scar pain, bandl ring, bleeding, maternal exhaustion.
• Follow-up: cervical examination 2-hourly on oxytocin; maternal temperature 4-hourly; bladder catheter for 24 hours after caesarean section; counselling about the next birth; review at 6 weeks.