EFFECTS OF LOW-FREQUENCY MAGNETIC-FIELDS ON FETAL DEVELOPMENT IN RATS

We studied effects of alternating magnetic fields on the embryonic and fetal development of rats. Mated females of the Han:Wistar-strain wer e sham exposed or exposed continuously to a 50-Hz field or to a 20,000 pulse-per-second (pps) sawtooth magnetic field from day 0 to day 20 o f pregnancy for 24 h/day until necropsied on day 20. The respective pe ak-to-peak intensities of the fields were 35.6 muT (sinewave) and 15.0 muT (sawtooth). Each treatment group contained 72 bred females. Contr ol animals were kept under the same conditions without the magnetic fi eld. No adverse effects were seen in the dams. The mean numbers of imp lantations and living fetuses per litter were statistically significan tly increased in the 50-Hz group. There were, however, three total res orptions of litters in dams of the control group, which contributed to the difference in the number of living fetuses. The corrected body-ma ss gains (gains without uterine content) of dams were similar in all g roups. Pregnancy rates, incidences of resorptions, late fetal deaths, and fetal body masses were similar in all groups. The incidence of fet uses with minor skeletal anomalies was statistically significantly inc reased in both exposed groups. Only one serious malformation (anophtha lmia, sawtooth-exposed group) and a few minor visceral malformations w ere found. In conclusion, the magnetic fields used in this study did n ot increase the incidence of major malformations or resorptions in Wis tar rats. The increased number of skeletal anomalies and implantations we observed indicates, however, that some developmental effects in ra ts may attend exposure to time-varying magnetic fields.