Arrested second stage with occipitoposterior position and recurrent variable decelerations
A 29-year-old nullipara at 40+5 weeks was admitted for induction of labour for post-term pregnancy. After 14 hours of oxytocin-augmented labour with epidural analgesia she is fully dilated, and the second stage has now lasted 2 hours 10 minutes. The head is at station −1 in occipitoposterior position, with marked caput succedaneum. Ultrasound two days earlier estimated fetal weight at 3,720 g; her height is 158 cm and weight 78 kg, and the pelvis was assessed as clinically adequate at admission. The bladder has just been emptied. The CTG shows a baseline of 145 bpm with recurrent variable decelerations to 75–80 bpm lasting 60 seconds and recovering within 30 seconds, without tachycardia and without reduced variability. Contractions are four in ten minutes. The consultant obstetrician and the theatre team are on site and a neonatal resuscitation team is available. The woman is exhausted but has been pushing effectively, and says she cannot continue for another hour. Fetal scalp blood sampling is available on the unit.
1. Interpret the CTG and the obstetric findings, and set out the realistic delivery options with your recommendation. What additional information would you want at the bedside before deciding?
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Interpretation: the CTG is abnormal in the sense of recurrent variable decelerations with a normal baseline and preserved variability - not an immediate 'deliver in the next five minutes' pattern, but also not reassuring enough to simply wait another hour. The mechanical picture is the driver: a nullipara at 2 h 10 min of active pushing (with epidural the accepted upper limit is about 3 hours, so she is not yet at the absolute limit), an unengaged head at station −1, occipitoposterior position and significant caput. An unengaged, malpositioned head after two hours of pushing predicts a high failure rate for vacuum extraction and a real risk of shoulder dystocia or a long, traumatic extraction.
Options
- Manual rotation to occipitoanterior and re-assessment, then either spontaneous pushing or vacuum extraction.
- Vacuum extraction from −1 in occipitoposterior position.
- Caesarean section in theatre.
- Fetal scalp blood sampling to refine fetal status before committing to a route.
Recommendation: Fetal scalp sampling has a role only if it will change management; here the maternal and mechanical parameters already argue against a difficult mid-cavity extraction. The safest plan is a category 2 caesarean section by a senior operator, with the theatre team already present, while an experienced operator may attempt manual rotation if the head descends to at least station 0 on the next contraction. Proceed to section if no descent.
Bedside information needed: exact station and asynclitism, degree of moulding, whether the head is palpable abdominally, adequacy of analgesia, uterine activity, consent status for both operative delivery and caesarean, and the neonatologist's presence.
2. Assume you decide to attempt a vacuum extraction. State the prerequisites you would confirm before applying the cup, the technique and the stopping rules, and what you would prohibit in the room.
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Prerequisites (check and document each)
- Full dilatation, membranes ruptured, bladder empty, adequate analgesia.
- Head engaged or at most station 0 with no more than moderate caput/moulding, position known, estimated fetal weight not macrosomic, and a pelvis judged adequate.
- No absolute contraindication: suspected cephalopelvic disproportion, unrecognised face or brow presentation, known fetal bleeding disorder such as haemophilia or alloimmune thrombocytopenia, prematurity where the fetal head is very fragile.
- Consent for operative vaginal delivery including the possibility of failure and conversion to caesarean, senior operator present, theatre and neonatal team immediately available, and a clear plan for how long the attempt may take.
Technique
- Choose an appropriate cup, place it over the flexion point, roughly 1–2 cm anterior to the posterior fontanelle in an occipitoposterior head, and check no maternal tissue is caught.
- Build negative pressure gradually to about 500–600 mmHg, then apply traction in line with the pelvic axis, synchronised with contractions, with the mother pushing.
- Between pulls, auscultate or review the CTG.
Stopping rules: abandon after three pulls, after about 15–20 minutes, after two pop-offs, or at any point where there is no descent with each pull. Then move to caesarean section or, if the head is genuinely at the outlet and the operator is trained, to forceps - never to a second vacuum.
Prohibited: fundal pressure (Kristeller) and any abdominal pushing, rotation with the cup, prolonged traction between contractions, and continuing 'just one more pull' in the face of no descent.
3. The woman, after explanation, declines operative vaginal delivery and asks for a caesarean section. How do you handle consent, timing and documentation, and what would you tell her about the risks of each route in her specific situation?
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Handling
- Accept her decision: a competent woman may refuse a vaginal operative delivery. Coercion or proceeding without consent would be both unlawful and clinically unwise.
- Explain that the CTG is not immediately terminal but that delivery should be expedited; caesarean section in the second stage is a more morbid operation than first-stage caesarean, with greater risk of extension into the lower segment, bladder injury, haemorrhage and infection, but it avoids the trauma of a likely failed extraction.
- Give the actual numbers for her case in plain language: mid-cavity vacuum in an occipitoposterior, unengaged head in a nullipara has a failure rate in the order of 10–30%; failed vacuum followed by caesarean roughly doubles the risk of maternal fever, transfusion and neonatal trauma compared with immediate caesarean. Caesarean section carries risks of haemorrhage, transfusion, VTE, wound and uterine infection, longer recovery and implications for future births.
- Obtain written consent for caesarean section, including consent for possible escalation such as uterine artery ligation, and for the paediatric team to attend.
Timing: category 2 caesarean - decision-to-delivery ideally within 30 minutes, with continuous CTG and the same level of fetal monitoring in the transfer to theatre; call the consultant, anaesthetist and neonatologist now.
Documentation: record the CTG findings over time, the obstetric findings (station, position, caput, moulding), the options offered, the discussion of risks, the patient's own words declining operative vaginal delivery, the consent, the time of decision and the names and grades of staff present. Also record that a senior obstetrician attended.