I have nothing on cervical cancer and I don't think there is any
evidence that breastfeeding does protect against it.  Here are some
articles on ovarian cancer.

Hartge P, Schiffman MH, Hoover R, McGowan L, Lesher L, Norris HJ. A
case control study of epithelial ovarian cancer. Am J Obstet Gynecol
1989;161:10-6
Gwinn ML, Lee NC, Rhodes PH, Layde PM, Rubin GL. Pregnancy,
breastfeeding and oral contraceptives and the risk of epithelial
ovarian cancer. J Clin Epidemiol 1990;43:559-68
Rosenblatt KA, Thomas DB, and the WHO collaborative study of neoplasia
and steroid contraceptives. Lactation and the risk of epithelial
ovarian cancer. International J Epidemiol 193;22:192-7

Jack Newman, MD, FRCPC