Disruption of embryonic and fetal development due to preimplantation chemical insults: a critical review.

Descriptive teratology has developed several fundamental precepts, two of which can now be challenged on the basis of experimental evidence. The first is that prior to implantation the developing embryo is not susceptible to survivable defects from chemical injury. The second is that developmental defects cannot be due to mutational events since rare events seem unlikely to explain alterations in large populations of cells. This review presents current experimental evidence demonstrating that the effects of chemical exposure on blastocyst stage embryos may be manifest long after the time of insult and that subtle nonlethal mutations may have a role in poor fetal performance after early chemical exposures.