Effects of microwaves on fetus and female genital organs remain to be elucidated. To demonstrate the placental circulatory disturbances induced by microwaves and to clarify the endocrine pathogenesis, placental blood flow and five endocrine indicators, i.e., corticosterone (CS), estradiol (E2), progesterone (P), prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) were measured in rats exposed to whole-body microwaves with an intensity of 10 mW/cm2 at a frequency of 2,450 MHz. The placental blood flow at 45-90 min after exposure was significantly decreased in the rats exposed to the microwaves. Placental blood flow at 15 and 30 min was increased by pretreatment with intraperitoneal administration of angiotensin II (AII). In contrast, no significant change in placental blood flow was recognized in the AII pretreated rats exposed to the microwaves. An increase in CS and a decrease in E2 were induced by the microwave exposure independent of pretreatment with AII. P was increased by microwave exposure in the rats without pretreatment with AII. PGE2 was not changed by the microwave exposure in the case of either nonpretreatment or pretreatment with AII. PGF2 alpha was increased by the microwave exposure in the rats without pretreatment with AII. The present results indicate that excessive exposure to whole-body microwave disorders pregnancy in terms of placental circulatory dysfunction. The data suggest the involvement of endocrine mechanisms in the decrease in placental blood flow which is induced via a detrimental effect of microwaves on PGF2 alpha and on pituitary functions such as general emotional stress.

With the recent remarkable development of transportation facilities, pregnant women are frequently exposed to mechanical vibration. To experimentally demonstrate that vibration disorders normal pregnancy, uterine blood flow (UBF) and the several kinds of endocrine indicators were examined in pregnant rats exposed to vibration (10m/s2, 8Hz, 90 min). The exposure to vibration decreased UBF in the rats significantly. The UBF of the rats pretreated with peritoneal administration of angiotensin II (AII) was increased when they were not exposed to vibration. In contrast to this, in AII pretreated rats simultaneously exposed to vibration, a significant decrease in the UBF was recognized. Vibration decreased the plasma level of progesterone (PRO), but pretreatment with AII induced no difference in PRO in vibration-exposed and unexposed rats. The level of prostaglandin E2 (PGE2) was decreased in rats exposed to vibration, but not in control rats. Pretreatment with AII still decreased PGE2 in rats exposed to vibration. These results indicate that vibration may play an important role in the development of abnormal pregnancy through uterine circulatory and ovarian dysfunctions. It seems that a decrease in UBF is induced primarily via an inhibitory effect of vibration on PGE2, and secondarily via a direct action on the uterus.