Transcription factors are differentially expressed during pregnancy in the livers of tg-CYP2D6 mice. Liver tissues were collected from tg-CYP2D6 mice at pre-pregnancy (virgin), 7, 14, and 21 days of pregnancy (G7, G14, and G21, respectively), or 7 days postpartum (PP7), and total RNA was isolated from the tissues. The mRNA expression levels of the respective transcription factors were determined by qRT-PCR (n = 4, mean ± S.D.; *P < 0.05, **P < 0.01 versus virgin).