Yesterday on Janet Parshall’s show a listener asked the question, “Does premature birth raise the risk of breast cancer?”
The answer in the literature is that it indeed does raise the risk of BC when the baby is born prior to 32 weeks. This is because of he same mechanism associated with abortion. The termination of the pregnancy prior to 32 weeks leaves the mother with more immature breast cells where cancer can start.
However, the effects of placental lactogen begin in the mid-late second trimester and by 32 weeks, 90% of the cells that will become cancer resistant Type 4 cells have already been converted. So the risk increases as we move backward from 32 weeks to earlier weeks.
The following studies are helpful:
Melbye M, Wohlfahrt J, Andersen A-M N, Westergaard T, Andersen PK. Preterm delivery and risk of breast cancer. Bri J Cancer 1999;80:609-13.
Hsieh C-c, Wuu J, Lambe M, Trichopoulos D, et al Delivery of premature newborns and maternal breast-cancer risk. Lancet 1999;353-1239.
Vatten LJ, et al. Pregnancy related protection against breast cancer depends on length of gestation. Br J Cancer 2002;87:289-90.
Innes K and Byers T. First pregnancy characteristics and subsequent breast cancer risk among young women. Int J Cancer 2004; 112:306-311.