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.
Coming Home 
Wait, so this applies only to women who gave birth prematurely, and not the preemie baby? Or does the BC risk also apply to the preemie baby, if the baby is a girl?
(I ask this because I was born prematurely by C-section, at around 6-7wks early, because my mother had toxemia.)
I realize that means I was born at around 34 wks, which makes the 32-wks cutoff mentioned above, but I guess it still seems so close to me. 😛
Forgive me my ignorance! 🙂
However, I must say this is all very interesting, how gestation can relate to BC and all. Would the risk also apply to women who miscarried?
Thanks for the list of studies. One of my children was born at 26 weeks, and I have been concerned about this as an unknown variable.
Do subsequent pregnancies help reduce the risks caused by the premature birth?
Thank you! I hope Delores finds this. ( on the previous post.)
Bless you from our Gracious and great LORD! ~Julia
Hmmm, then perhaps what my doctor in Tokyo said was correct — that miscarriages can indeed raise BC risk, depending on hormone levels.
(Not that I have wasted time worrying about it.)
Dr. Nadal in regards to you talk on 10/15/2010 about breast cancer and premature births I found fascinating,could you direct me to more resources about this topic.Thank you
Tom, I just got in from a lecture a few hours away from home (2:40 AM) I’ll dig out the references tomorrow.