Intended for healthcare professionals


Maternity care: Entonox is withdrawn from some hospitals because of risk to staff from high exposure

BMJ 2023; 380 doi: (Published 27 January 2023) Cite this as: BMJ 2023;380:p212
  1. Jacqui Wise
  1. Kent

The Princess Alexandra Hospital in Harlow, Essex is the latest to suspend the use of Entonox in its maternity unit after air quality tests found levels of nitrous oxide that may put midwives and other healthcare workers at potential risk of harm.

The Health and Safety Executive is already investigating Basildon Hospital, which temporarily stopped using Entonox in December 2022. A BBC report said that nitrous oxide levels found during air sampling were 30 times the legal limit.1

The Royal College of Midwives is considering legal action to support midwives working at Basildon, who have reported a variety of symptoms they attribute to exposure to Entonox.

Entonox, which consists of 50% oxygen and 50% nitrous oxide, has been used for many years as a pain relieving gas mixture. Suspending its use limits the options available to women during childbirth. Alternatives tend to have more side effects and could lead to more interventions during delivery.

Although nitrous oxide is considered a safe option for pain relief during childbirth, prolonged exposure to the gas could lead to vitamin B12 deficiency and anaemia and has been linked to fertility problems. Studies of healthcare workers have investigated whether nitrous oxide increases the risk of miscarriage or produces adverse effects on the fetus, but there …

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