Obstetric anaesthesia · Core16 / 17
Preterm birth on magnesium with neonatal resuscitation25-year-old woman, 60 kg, in preterm labour at 29 weeks; vaginal birth is imminent
Preterm delivery: neonatal resuscitation algorithm from ventilation to compressions
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Know this first
- Magnesium before 34 weeks reduces cerebral palsy; it is not used as a tocolytic alone.
- Newborn temperature 36.5–37.5 °C; plastic wrap and radiant warmer for preterm babies.
- Under 32 weeks, start ventilation with 30–100% oxygen.
- Compressions if HR stays under 60 after 30 seconds of effective ventilation; 3:1.
- Adrenaline 0.01–0.03 mg/kg IV, every 3–5 minutes.
The patient
25-year-old woman, 60 kg, in preterm labour at 29 weeks; vaginal birth is imminent.
Magnesium sulfate for fetal neuroprotection after a 4 g load; two doses of betamethasone given; labour epidural working.
Otherwise well.
Vitals: BP 110/66, HR 96, SpO2 98% on air, RR 16.
The examiner asks
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Consider
What are the issues?
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- A 25-year-old in preterm labour at 29 weeks, on magnesium, about to deliver vaginally. Patient
- At 29 weeks she has caval compression and aspiration risk if a caesarean becomes urgent.
- Magnesium before 34 weeks protects the baby's brain; it isn't her tocolytic. Disease
- In her, magnesium worsens hypotension and strengthens any muscle relaxant.
- A preterm baby is drug-sensitive, but asphyxia and birth trauma matter far more.
Plan
How do you prepare for the birth?
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- Neonatal team present with a warmed resuscitaire, plastic wrap and a hat. Patient
- A warm room; the baby's temperature kept between 36.5 and 37.5 °C.
- Cord clamping deferred at least 60 seconds if the baby needs no immediate help. Surgery
- Under 32 weeks, ventilation starts with 30–100% oxygen, titrated to saturation. Disease
- For her: low-dose epidural, with reflexes, breathing and BP watched on magnesium.
Crisis
The baby is born floppy and apnoeic, heart rate about 80/min. What do you do?
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- NRP: apnoeic preterm baby, heart rate under 100, so positive pressure ventilation now. (Crisis)
- Under the radiant warmer in the plastic wrap; airway opened, inflation breaths given.
- Start at 30% oxygen with a preductal oximeter.
- A rising heart rate tells me ventilation works; ECG gives the fastest accurate rate.
- No rise: correct mask seal and airway position, then laryngeal mask or tube.
Crisis
Despite 30 seconds of ventilation through a tube that moves the chest, the heart rate is 50/min. What do you do?
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- Heart rate under 60 after effective ventilation: start chest compressions. (Crisis)
- Two-thumb encircling technique, 3 compressions to 1 breath: 90 and 30 a minute.
- Oxygen raised to 100% during compressions, then titrated down after.
- Umbilical venous catheter for access; intraosseous if that fails.
- Still under 60: adrenaline 0.01–0.03 mg/kg IV, repeated every 3–5 minutes.
- Volume 10–20 mL/kg if blood loss is suspected.
Fatal mistakes
- Starting compressions before effective ventilation.
- Letting the preterm baby get cold.
- High oxygen without saturation targets.
Checked against: Barash 9e · AHA and AAP guidelines: neonatal resuscitation (2025)
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