N2O Absolute Contraindications — ORE Part 1 MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: A — First trimester of pregnancy
**A is correct.** First-trimester pregnancy is listed in UK dental sedation guidance as a contraindication to nitrous oxide inhalation sedation. The concern is avoidance of non-essential nitrous oxide exposure during early fetal development; elective care requiring sedation should therefore be deferred or managed by an alternative approach where appropriate. Mild dental anxiety is instead a principal indication for inhalation sedation. Age over 50 years is not a contraindication: suitability depends on medical status and assessment rather than chronological age. Having previously accepted dentistry without sedation does not determine present sedation suitability. Well-controlled mild asthma is not, by itself, a contraindication; the patient should nevertheless undergo routine pre-sedation assessment and be clinically stable on the day of treatment.
Reference: Royal College of Surgeons of England. UK National Clinical Guidelines in Paediatric Dentistry: Managing anxious children: the use of conscious sedation in paediatric dentistry, 2002, section 2.1.2 “Contra-indications”. https://www.rcseng.ac.uk/-/media/files/rcs/fds/publications/paed_sedation.pdf?la=en