Physical therapists (females) occupationally exposed to 27.12, 915, and 2450 MHz MW from medical diathermy units were reported to have an increased incidence of miscarriages. An exchange of letters between Hocking & Joyner and Ouellet-Hellstrom & Stewart (Am J Epidemiology (1995) 141(3):273-274; Am. J. Epidemiology (1995) 141:274), specifically regarding the authors suggestion that tissues with higher water content such as amniotic fluid are more susceptible to energy deposition by microwaves. Hocking & Joyner further stated that the depth of penetration for 27.12, 915, and 2450 MHz MW is 14.3, 3.04, and 1.7 cm, respectively, and that the maximal SARs in the uterus given this penetration depth would only be 0.209, 0.023, and 0.000027 W/kg, respectively. Ouellet-Hellstrom & Stewart, however, claim the observations were statistically significant with a dose response relationship, are consistent with previous evidence, and that depth of penetration may not be the only factor explaining the findings.