Repetitive exposure of mice to strong static magnetic fields in utero does not impair fertility in adulthood but may affect placental weight of offspring.

Purpose: To investigate the effect of daily exposure in utero to static magnetic fields during prenatal development on germ cell development and fertility of exposed offspring in adulthood.

Materials And Methods: Mice were exposed daily in utero to different static magnetic field strengths at the bore entrance or in the isocenter of 1.5 T and 7 T MRI systems during the entire course of prenatal development.

Results: In utero-exposed male mice revealed no effect of magnetic field strength on weight of testes and epididymis or on sperm count, sperm morphology, or fertility. Exposed pregnant female mice showed no reduced fertility in terms of pregnancy rates and litter size, pointing to a normal ovarian function. However, a reduced placental weight of offspring of intrauterine exposed female mice was observed that correlated with a decrease in embryonic weight in those animals exposed at the strongest magnetic field. This effect seemed to be parent-dependent, since it was not observed in those embryos fathered by in utero-exposed male mice.

Conclusion: Repetitive in utero exposure to strong static magnetic fields does not impair fertility but may have a parental-dependent effect on fetal programming with regard to placental development and fetal growth.