(A) Fertility of Dicer^d/d female mice transplanted with Dicer^+/+ ovaries. Ovaries of Dicer^d/d and Dicer^+/+ littermate mice were exchanged (n = 8 pairs), and the mice were subsequently bred to wild-type fertile males. Delivery rate and average litter size are shown. (B and C) Ovulation and fertilization were normal in Dicer^d/d mice. (B) Representative morphologies of the 2 cell embryos collected from the oviducts of Dicer^d/d mice on day 1.5 after coitus. Original magnification, ×100 (top), ×400 (bottom). (C) Rates of ovulation and fertilization in Dicer^d/d and Dicer^+/+ mice were examined on day 1.5 with or without superovulation. (D) Serum progesterone levels were lower in Dicer^d/d mice during pregnancy. Serum levels of progesterone in Dicer^d/d mice were determined by ELISA on days 1.5, 5.5, and 7.5 of pregnancy and expressed as mean ± SD (n = 3). (E) The expression of genes associated with CL function was lower in Dicer^d/d mice. Semiquantitative RT-PCR analyses of luteinizing hormone receptor, prolactin receptor, and cytochrome P450 family 11 subfamily a polypeptide 1 mRNA in ovaries of Dicer^d/d and Dicer^+/+ mice were conducted on days 1.5, 5.5, and 7.5 after coitus. Results from 2 separate littermate samples are shown.