Why is having fewer pregnancies or fewer kids a risk factor for cancer of the breast?

Estrogen exposure. Prolonged exposure to and higher concentrations of estrogen increases the risk of breast cancer. The more pregnancies the fewer menses. Breast feeding accomplishes the same goal. Also age at 1st birth is associated with bc risk too. Check this out from acs: http://bit.Ly/oysxjs.
Later pregnancies . Pregnancy is protective against cancer because there is a natural change in hormone fluctuations. The estrogen produced in pregnancy, estriol is very protective against breast cancer. However this occurs only if the pregnancy occurs before 30, not after. Breast feeding stops the hormones which can also be protective; so its age, how often pregnant and breast feeding that are the factors to see.
Unknown. "risk factor" refers to a statistical association between two items. We can postulate why , but those at best are informed guesses. With out a controlled scientific experiment , we do not know the true answer. Statistics can mislead us.

Related Questions

I read on a site that there are rare chances of having breast cancer in pregnancy. Is the risk higher?

Probably not. Breast cancer may occur during pregnancy but it is unlikely that pregnancy is a risk factor. See this site for more info. http://www.cancer.org/cancer/breastcancer/moreinformation/pregnancy-and-breast-cancer. Read more...

Can pregnancy induce breast cancer?

Less likely. Pregnancy causes many hormone changes in the body. For one thing, pregnancy stops monthly menstrual cycles and shifts the hormone balance toward progesterone rather than estrogen. This is why women who become pregnant while they are young and have many pregnancies may have a slightly lower risk of breast cancer later on. They are exposed to less estrogen. Women who have had no children or who had their first pregnancy after age 30, on the other hand, have a slightly higher breast cancer risk. Read more...

What're the chances of pregnancy after radiation therapy on breast cancer?

Depends on age. Radiation therapy of the breast does not affect the ovaries. This means that if you are still having periods, you can become pregnant if you do not use protection. If you are also having chemotherapy and are close to menopause, the chemo can put you into menopause then the chances of pregnancy are slim. Read more...
No effect . Radiation therapy to the breast has not been shown to reduce your fertility. That said, it is important to use birth control methods during radiation therapy to prevent pregnancy during treatment. Read more...

Is there a connection between women who have late pregnancies and breast cancer?

Yes. Analysis of statistics shows women who have earlier age at first menstrual cycle, first childbirth at a later age & those who do not breast feed can have higher risks of breast cancer. But does not mean that all of those will get breast cancer. Read more...

What is the likelihood of pregnancy for a young woman receiving breast cancer treatment?

Depends. on treatments , if receiving only local radiation ovulating woman can get pregnant , if receiving chemotherapy will not ovulate most of the time will be permanently sterile Speak to your doctor. Read more...

If you had undiagnosed breast cancer and then got pregnant, would the pregnancy hormones shrink the tumor?

NO. The very high hormone levels of pregnancy are a big risk factor for increased growth, and often, women with a breast cancer diagnosis have to deliver their babies early, so that they can have their evaluation for the cancer completed, or surgery done, and begin any additional treatments necessary. Read more...

Does having a miscarriage (when the body naturally aborts a pregnancy) increase my chances of breast cancer?

No. There is no scientific evidence in the gynecologic medical literature that miscarriage - whether spontaneous such as a miscarriage, or induced, such as with an elective abortion - is in any way associated with an increased risk of breast cancer or any other malignancy for that matter. Read more...
No. This does not increase your risk for breast cancer. I'm sorry for your loss. I know this is a difficult time for you and your family. Best of luck in the future. Read more...