Occupational Exposure: One legitimate concern is the occupational exposure of midwives and other workers to nitrous oxide. Midwives exposed to nitrous oxide (continuously, over 7.5 to 11 hour shifts) in older, unventilated hospitals in the U.K. had chronic exposures in excess of U.S. OSHA limits.(U.S. OSHA guidelines are more stringent than those of most other countries.) This could lead to reduced fertility in female workers.
However, midwives in newer hospitals with modern ventilation were found to have levels well below U.S. OSHA limits, even when the hospitals did not use scavenging equipment. Other studies of hospitals/birth centers/dental clinics have shown low levels of exposure when scavenging equipment is used. According to Dr. Rosen, the key is to use scavenging equipment; even if nitrous oxide is relatively safe, why not just get rid of it, so workers do not have to worry about occupational exposure? Scavenging equipment is a standard part of modern nitrous oxide equipment for laboring women.
Apoptosis: Another concern that has been expressed is that of apoptosis, the type of natural cell death that protects us from cancer, but can be a problem when taking place unnaturally. Unlike the real-world issue of occupational exposure to nitrous oxide, this effect has only been seen in laboratory animal studies at doses approximately 50 times that a laboring woman would ingest, a dose women in labor would never receive. (In fact, hyperbaric chambers had to be used to deliver the continuous, six-hour superatmospheric doses used in these experiments, since it is impossible to achieve a dose this high at normal atmospheric pressure.) Since many/most drugs in use have much more serious effects (e.g., death) at far lower than 50X effective-doses, this actually reflects the safety of nitrous oxide, especially compared with other analgesics.
Mild analgesia: Many feel that the reason for nitrous oxide's lack of availability here is that it is only a mild-to-moderately effective form of analgesia, in contrast to the very strong effects of an epidural. Judith Bishop, a midwife who works with nitrous oxide at the UCSF Moffitt hospital in San Francisco, states that "Not all laboring women who try it find it useful. Those who do either report reduced pain or acknowledge they are still in pain but care less about it." There is a prevalent idea that women do not want a mild form of pain relief that is only somewhat, rather than 100%, effective, but this presupposes that all women want 100% pain relief, unless they want to be 100% drug-free, and does not acknowledge the true diversity of women and their birth wishes.
Laboring women are often grouped together as one homogenous bloc, but in fact, the birth wishes of pregnant women are as diverse as the women themselves. With respect to pain relief, many women do want complete anaesthesia. "Knock me out -- I don't want to feel anything!" is a common refrain for many pregnant mothers-to-be. For these women, the highly medicalized birth options available in the U.S. are perfect. Complete anaesthesia through an epidural can enable an easy birth, and many mothers have been quite happy with this option.
At the other end of the spectrum are women who want a completely unmedicated birth, with no drugs of any kind. This option is becoming increasingly available, through alternative birthing centers, home-birth midwives, and more progressive, patient-centered hospitals. Many health professionals believe that all women are at either one or the other end of this spectrum.
However, there are other women who want to have a birth that is as natural as possible, but also would like "just a little" pain relief to help them achieve their goal. This is the strength of nitrous oxide. As midwife Judith Rooks states, "Nitrous oxide is not right for every woman during labor, but it is wonderful for some women."
Dr. Claudia Copeland holds a Ph.D. in molecular and cellular biology, with a tropical medicine emphasis, including the equivalent of a masters' degree in public health. She has given birth naturally twice, and would like to increase the availability of information for other women interested in minimizing excessive medical intervention for childbirth.