Nitrous oxide and spontaneous abortion in female dental assistants

Am J Epidemiol. 1995 Mar 15;141(6):531-8. doi: 10.1093/oxfordjournals.aje.a117468.


The relation between anesthetic gas exposure and spontaneous abortion remains unresolved. We examined the effect of nitrous oxide on spontaneous abortion among female dental assistants. Questionnaires were sent to 7,000 dental assistants aged 18-39 years who were registered in California in 1987; 4,856 (69%) responded. Analysis was based on 1,465 respondents whose most recent pregnancy was conceived while working full time. Women were asked how many hours a week they worked with nitrous oxide during this pregnancy and whether the excess gas was scavenged (vented). Relative risk of spontaneous abortion (through week 20) was calculated using a person-week model. This allowed women with current pregnancies (13%) or induced abortions (10%) to be included for appropriate time periods of risk. A total of 101 pregnancies (7%) ended as spontaneous abortions. An elevation in risk of spontaneous abortion was seen among women who worked with nitrous oxide for 3 or more hours per week in offices not using scavenging equipment (relative risk = 2.6, 95% confidence interval 1.3-5.0, adjusted for age, smoking, and number of amalgams prepared per week), but not among those using nitrous oxide in offices with scavenging equipment. This relation changed little when analyses were restricted to confirmed pregnancies or examined for several types of potential bias. Scavenging equipment appears to be important in protecting the reproductive health of women working with nitrous oxide.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Abortion, Spontaneous / chemically induced*
  • Abortion, Spontaneous / epidemiology
  • Adolescent
  • Adult
  • Air Pollution, Indoor / adverse effects*
  • Bias
  • California / epidemiology
  • Cohort Studies
  • Dental Assistants*
  • Female
  • Gestational Age
  • Humans
  • Multivariate Analysis
  • Nitrous Oxide / adverse effects*
  • Occupational Exposure / adverse effects*
  • Pregnancy
  • Pregnancy Outcome
  • Risk
  • Surveys and Questionnaires


  • Nitrous Oxide