ESPN says Miller is due this summer with her second child. She and husband John Falconetti also have a 3-year-old son, Rocco.
In late 2010, the two-time world all-around champion, was hoping to get pregnant again when doctors discovered a germ cell malignancy, a form of ovarian cancer
The National Cancer Institute says germ cell tumors begin in the reproductive cells (egg or sperm) of the body. Ovarian germ cell tumors usually occur in teenage girls or young women and most often affect just one ovary.
The ovary with the tumor was removed in January 2011, and Miller then had nine weeks of chemotherapy. She says she is now cancer-free.
Miller won seven Olympic medals and nine at the world championships.
For more on germ cell ovarian cancer, click here.