Hi Ladydiver:
I'm not Dr. Deco, but I do have some info that might help. Hope you don't mind me jumping in.
Maida Beth Taylor, MD wrote a chapter in Bove and Davis' DIVING MEDICINE that includes a discussion on Diving, Hyperbarics, and Pregnancy. She lists several reasons why women should not dive while pregnant. While a fetus seems to be at no increased risk for developing DCS than the mother, (and may even be at decreased risk) (1-4) the risk to the fetus if it does develop DCS may be significant. Animal studies in sheep show a high risk of fetal death if DCS is induced in the fetus (but studies in dogs and rats do not.) Since the fetal blood is oxygenated by the placenta, there are shunts around the fetus' lungs (patent foramen ovale and ductus arteriosus.) Because of these shunts, fetuses lack the filtering qualities of the lungs for bubbles. If bubbles do form in DCS the bubbles are more likely in a fetus to reach a vital organ. Most animal studies are done at depths that far exceed recreational diving limits (6.4-7.1 ata.)
I do not know of any studies on Arterial Gas Embolism (AGE) in diving, but the literature shows a very high rate of death in both mother and fetus in cases of AGE in non-diving incidents.
Because of the potential for increased risk to the fetus from diving you can't ethically ask pregnant women to dive for your study. But two studies in humans that surveyed pregnant women after they went diving have been done. One study showed no increased risk of birth defects or fetal loss. (5) The other suggested a higher incidence of low birth weight, birth defects, neonatal respiratory difficulties, and other problems in the group that continued diving perinatally, but a statistical analysis was not done. (6) The more severe (heart) abnormalities were associated with deeper diving (120-160 ft.)
The bottom line is that we don't know for sure what the effects of diving are on the human fetus. The risk is probably low in typical recreational diving not associated with DCS or AGE, but the potential injuries could be severe. I would say, NO do not dive while pregnant. It's not worth the potential risks. But if you do dive and then later find out you were pregnant, don't sweat it too much.
Bill
References
1.McIver RG, et. al.: Bends resistance in the fetus. In Preprints of scientific program. Annual Scientific Meeting. Washington, DC, Aerospace Medical Association, 1968
2. Neimiroff MJ, et. al.: Multiple hyperbaric exposure during pregnancy in sheep. Am J Obstet Gynecol 140:651, 1981
3. Powell MR, et. al.: Fetal and maternal bubbles detected noninvasively in sheep and goats following hyperbaric decompression. Undersea Biomed Res 12:59-69, 1985
4. Wilson JR, et. al.: Hyperbaric exposure during pregnancy in sheep: Staged and rapid decompression. Undersea Biomed Res 10:10-15, 1983
5. Bangasser SA: Medical profile of the woman scuba diver, In National Association of Underwater Instructors Proceeding of the 10th International Conference on Underwater Education, Colton, CA, NAUI, 1978, pp 31-40
6. Bolton ME: Scuba diving and fetal well-being: A survey of 208 women. Undersea Biomed Res 7: 183-189, 1980