Twenty-eight percent became pregnant the first menstrual cycle. The rate of conception declined as the number of cycles increased. Twenty percent of the dental assistants in California work in offices without scavenging. This data suggests that exposure to high levels of unscavenged nitrous oxide can impair fertility. Between 30 and 50 percent of dentists use nitrous oxide.
Most dental assistants are women of child bearing age.
As the hours of exposure to nitrous oxide increase for a woman trying to become pregnant, fertility decreased. However, offices using scavenging, or limiting exposure to less than 5 hours per week had no change in infertility from the unexposed. This study is the first to look at this issue. It was well done and well controlled for covariates that might have also been associated with a decrease in fertility. While retrospective studies are vulnerable to criticism and response bias has been a problem in reproductive studies involving anesthetic gasses, this study endeavored to control such effects.