Teratogenic effects of repeated exposures to X-rays and/or ultrasound in mice

Pregnant Swiss mice were exposed to 9 mGy of 70 kVp X-rays or 10 min of ultrasound (3.5 MHz, ~65 mW, I_SPTP = 1 W/cm², I_SATA = 240 mW/cm²) on Days 6.5 and 11.5 of gestation in four combinations: X-rays on both days (X + X), ultrasound on both days (U + U), X-rays on Day 6.5 postcoitus (PC) and ultrasound on day 11.5 PC(X + U) and ultrasound at 6.5 days PC and X-rays on day 11.5 PC(U + X). Sham-treated controls were maintained for comparison. Effects on prenatal development, postnatal growth and adult behavior were studied. U + U group showed an increase in percent growth retarded fetuses and a nonsignificant increase was seen in the U + X group. Transient growth retardation was observed in all the exposure groups. This is less likely to be of any biological significance as the animals recovered during postweaning period. The postnatal mortality was significantly higher only in the U + U group. In the X + U group, the exploratory activity was affected at 6 months of age. There was a significant change in the locomotor activity with a reduction in the total activity at 3 and 6 months of age in the U + U group. Latency in learning capacity was also noticed in this group. The results indicate that repeated exposures to ultrasound or its combination with X-rays could be detrimental to the embryonic development and can impair adult brain function when administered at certain stages of organogenesis.