Pro-Con Debate: Nitrous Oxide for Labor Analgesia

Table 1

Nitrous oxide relative contraindications during pregnancy.

Condition		Prevalence
Metabolic Risk
	Low vitamin B12	29%
	Low folate	6.4%
	Hyper Homocysteinemia	21%
Genetic Risk
	MTHFR homozygous polymorphisms 677C>T, 1298A>C	20% western Europe
	Non-Hispanic white CDC	22%
	Non-Hispanic black CDC	4.6%
	Mexican American CDC	23.4%
	Fetal MTHFR polymorphism	Consider parental heritage
Cardiovascular risk
	Preeclampsia spectrum	5-10%
	Hypertension 20-44 y.o.F	10.4%
	Hypercholesterolemia; 20-44 y.o. F	9%
Drugs of Abuse (NMDA Antagonists) history
	Ethanol use pregnancy CDC	10%
	Phencyclidine/hallucinogen	0.5%
	Nitrous oxide general population	4-8%
	Nitrous oxide UK	Second to cannabis
Medical condition
Closed space (nitrous causes expansion)	e.g. COPD, asthma attack, occlusion of middle ear e.g. infection