A case-control study of parity, age at first full-term pregnancy, breast feeding and breast cancer in Taiwanese women.

A hospital-based case-control study was designed herein to investigate the relationship between parity, breast feeding and breast cancer in Taiwan. Reproductive histories of patients with breast cancer confirmed by either pathology or cytology were assessed by questionnaire and compared with age-matched healthy controls. One hundred and fourteen cases and 228 age-matched controls were recruited for this study. According to those results, women having had more than three full-term pregnancies, age at first full-term pregnancy younger than 30, and breast feeding for more than 3 years displayed significantly protective effects against breast cancer. Following adjustment for ethnicity and menopausal status, women with more than three full-term pregnancies and younger than 30 years old at first full-term pregnancy had a decreased risk of breast cancer. However, duration of breast feeding was not related to breast cancer, after adjustment for ethnicity and menopausal status. The effect of number of full-term pregnancies on the risk of breast cancer was found to be independent of the effect of age at first full-term pregnancy. Moreover, the effect of age at first full-term pregnancy and number of full-term pregnancies was also independent of the effect of breast feeding.