Relationship between low midazolam metabolism by cytochrome P450 3A in mice and the high incidence of birth defects.

The use of midazolam in early stages of pregnancy has resulted in a high incidence of birth defects; however, the underlying reason is unknown. We investigated expression changes of the CYP3A molecular species and focused on its midazolam metabolizing activity from the foetal period to adulthood. CYP3A16 was the only CYP3A species found to be expressed in the liver during the foetal period.