Prescribing During Labour

Prescribing in labour covers induction and augmentation, analgesia, infection prevention, management of hypertensive disease and prevention and treatment of postpartum haemorrhage. Doses act within minutes and affect both mother and neonate, so timing relative to birth is as important as the dose.

Uterotonic risk. Excessive uterine activity (more than 5 contractions in 10 minutes) reduces placental perfusion and risks foetal hypoxia and uterine rupture, especially with a previous caesarean scar.

Neonatal effects. Opioids given within 1 to 4 hours of birth cause neonatal respiratory depression; magnesium can cause neonatal hypotonia.

Postpartum haemorrhage. Blood loss of 500 mL or more within 24 hours; a leading cause of maternal death in East Africa. Active management of the third stage is a core prescribing task.

Cervical ripening and induction.

• Dinoprostone vaginal tablet or gel 3 mg (1 mg gel in some settings), repeat 3 mg after 6 hours if needed; maximum 6 mg. Alternative: 10 mg controlled-release vaginal insert left for up to 24 hours.
• Misoprostol 25 micrograms orally every 2 hours, or 25 micrograms vaginally every 4 hours; do not use with a previous caesarean or uterine scar.
• Mechanical methods (balloon catheter) suit a scarred uterus.

Oxytocin infusion. 10 units in 500 mL sodium chloride 0.9% (20 milliunits/mL). Start at 1 to 2 milliunits/minute and increase by 1 to 2 milliunits/minute every 30 minutes until 4 contractions in 10 minutes. Usual maximum 20 milliunits/minute; up to 32 milliunits/minute under senior review. Start at least 6 hours after the last prostaglandin.

Analgesia.

• Nitrous oxide 50% in oxygen by inhalation as needed.
• Pethidine 50 to 100 mg IM, repeated after 1 to 3 hours; maximum 2 doses. Alternative: morphine 5 to 10 mg IM. Give an antiemetic.
• Remifentanil patient-controlled IV analgesia, bolus 20 to 40 micrograms with 2-minute lockout, only with continuous one-to-one midwifery care and oxygen saturation monitoring.
• Epidural: low-concentration bupivacaine or levobupivacaine 0.0625 to 0.1% with fentanyl 2 micrograms/mL, by programmed intermittent bolus or patient control.

Group B streptococcus prophylaxis. Start at the onset of labour or membrane rupture, ideally at least 4 hours before birth.

• Benzylpenicillin 3 g IV, then 1.8 g every 4 hours until birth (alternative: 5 million units then 2.5 to 3 million units every 4 hours).
• Mild penicillin allergy: cefazolin 2 g IV, then 1 g every 8 hours.
• Severe penicillin allergy: clindamycin 900 mg IV every 8 hours if sensitive; otherwise vancomycin 20 mg/kg IV every 8 hours (maximum 2 g a dose).

Caesarean birth. Cefazolin 2 g IV (3 g if 120 kg or more) within 60 minutes before skin incision; in labour or after membrane rupture some units add azithromycin 500 mg IV. Severe penicillin allergy: clindamycin 900 mg IV with gentamicin 5 mg/kg IV.

Third stage prevention. Oxytocin 10 units IM (or 5 units slow IV) after birth of the baby. Heat-stable carbetocin 100 micrograms IM or IV over 1 minute is an alternative where cold chain is unreliable. Oxytocin 5 units with ergometrine 500 micrograms IM is an option without hypertension.

Postpartum haemorrhage treatment.

• Oxytocin 5 units slow IV, repeat once; then 40 units in 500 mL sodium chloride 0.9% at 125 mL/hour.
• Ergometrine 500 micrograms IM (or 250 micrograms slow IV), repeat after 15 minutes; maximum 1 mg.
• Carboprost 250 micrograms deep IM every 15 minutes; maximum 8 doses (2 mg).
• Misoprostol 800 micrograms sublingually as a single dose.
• Tranexamic acid 1 g IV over 10 minutes within 3 hours of birth; a second 1 g dose if bleeding continues after 30 minutes or restarts within 24 hours.

Contraindications. Ergometrine in hypertension, pre-eclampsia, cardiac disease and severe peripheral vascular disease. Carboprost in asthma. Misoprostol and dinoprostone for induction with a uterine scar. Oxytocin with malpresentation, placenta praevia or obstructed labour.

Oxytocin hazards. Tachysystole, uterine rupture, hypotension with rapid IV bolus (give 5 units slowly), water intoxication and hyponatraemia with prolonged high-dose infusion in large volumes of hypotonic fluid.

Interactions. Opioids with magnesium sulphate or benzodiazepines increase respiratory depression. Prostaglandins increase sensitivity to oxytocin. Ergometrine with macrolides, protease inhibitors (ritonavir, cobicistat) or azole antifungals risks ergotism.

Neuraxial timing. No neuraxial block within 12 hours of a prophylactic low molecular weight heparin dose or 24 hours of a treatment dose; platelets 75 x 10^9/L or more for neuraxial procedures in most units.

Special groups.

• Pre-eclampsia: restrict total IV fluid to about 80 mL/hour to avoid pulmonary oedema; avoid ergometrine.
• Kidney impairment: avoid pethidine (neurotoxic metabolite norpethidine) and adjust gentamicin to levels.
• Obesity: cefazolin 3 g at 120 kg or more; early epidural is advised.
• Regional: heat-stable carbetocin and misoprostol matter where oxytocin cold chain fails.

Monitoring. Continuous foetal heart rate monitoring with oxytocin; contractions every 15 to 30 minutes. Maternal respiratory rate, sedation score and oxygen saturation after opioids. Blood loss measured, not estimated, after birth.

Adjustment. Reduce or stop oxytocin with more than 5 contractions in 10 minutes or a pathological foetal heart rate; give terbutaline 250 micrograms subcutaneously for persistent hyperstimulation.

Stopping rules. Stop prostaglandins once in established labour or with hyperstimulation. Do not give pethidine within 2 hours of expected birth where avoidable.

Referral and escalation. Postpartum haemorrhage over 1000 mL or ongoing bleeding after first-line uterotonics: call senior obstetric, anaesthetic and haematology support, start massive transfusion arrangements and prepare for surgical control.