Fetal loss in mice exposed to magnetic fields during early pregnancy.

The effects of low-frequency magnetic fields (MFs) on early pregnancy were studied in CBA/S mice. The magnetic field was a 20 kHz, 15 microT sawtooth. Pregnant females were divided into four groups, two control groups and two exposed groups. One group was exposed to MFs continuously from day 1 postconception (pc) until day 5.5 pc, and the other group was exposed continuously until day 7 pc. All animals were sacrificed on day 19 pc, the day before partus, and their uterine contents were analyzed. No significant increase in the resorption (early fetal death) rate was found in the exposed animals compared to the sham controls. In the group exposed during days 1.0-5.5 pc, the body weight and length of the living fetuses were significantly decreased. Except on day 3 pc (progesterone) and day 13 pc (calcium) in the treated groups, there were no significant differences in progesterone and calcium levels in peripheral blood. Implantation occurred on the same day in MF-treated and control animals.