Today’s topic: how the anti-choice camp uses bad science to imply that there’s a link between abortion and breast cancer. Yay for bad science and fear mongering!
Now, serious question: what would be the means of which an aborted pregnancy will lead to cancer? How would terminating a pregnancy cause mutations in DNA that would break a cell’s mechanisms to not divide out of control?
After all, what cancer is at a fundamental level is really, really screwed up DNA. And the screw up occurs in such a way that these cells will not respond to the body’s mechanisms to control cell division.
So how does abortion (whether medicated or surgical) cause a DNA screw up so bad that the cells will replicate out of control?
Women who experience at least one full term pregnancy in their lifetime develop four types of breast lobules (a lobule is a unit of breast tissue consisting of a milk duct and glands). During adolescence, the majority of lobdules are Type 1 and Type 2, which are immature and cancer susceptible. Throughout the first trimester of pregnancy, the number of Type 1 and Type 2 lobules rapidly increase. As a result, breasts have more sites for cancer to start. In the second trimester, the breast lobdules start maturing into Type 4 lobules, which are cancer resistant. By the end of the third trimester, 85% of the breast has fully matured. Only 13% of the lobules remain immature and cancer-susceptible, leaving fewer opportunities for cancer to start. After birth and weaning, Type 4 lobules regress to Type 3. There is evidence of permanent changes in the genes of Type 3 lobules which provide life-long cancer resistance.
Wait, what? Are they seriously arguing that there’s a special type of cell that is more resistant to DNA mutation, hence more resistant to cancer? And that they’re only produced if you’re pregnant and give birth?
Let’s go back and go over this paragraph bit by bit, because something sound wrong here and I want to find out what.
Women who experience at least one full-term pregnancy in their lifetime develop four types of breast lobules (a lobule is a unit of breast tissue consisting of a milk duct and glands). During adolescence, the majority of lobdules are Type 1 and Type 2, which are immature and cancer susceptible. In the second trimester, the breast lobdules start maturing into Type 4 lobules, which are cancer resistant.
So I guess now I get to talk about boobs?
Okay, to start off with, we’re talking about lobes and lobules. The difference between a lobe and a lobule is that a lobe is a clear anatomical division that we can see without the help of a microscope, whereas the lobule requires one.
The breast has around 15-20 lobes, and in each lobe, we have many lobules. Each lobdule has a milk duct, which is where breast milk is made. These ducts produce milk due to hormonal signals in a positive feedback loop (essentially: baby feeds on breast, hormones say “make more milk!”, breasts make more milk, baby gets milk, baby feeds more until baby is full and happy).
The breast undergoes changes during puberty (thelarche, or the development of the breasts), menstruation (which is why breasts feel more tender and whatnot shortly after one’s period), pregnancy, and menopause. These changes are induced by hormones secreted by the body, and this causes the breast to change in size and shape. Some medications mimic these same hormones, which causes the side effect of large breasts.
During the second and third trimester of pregnancy, hormones in the body jump start the development of the milk duct system that will (if the mother chooses to breastfeed) be used to feed the baby. Some of the changes in the breast include:
- Larger lobes and alveoli (basically glands) thanks to progesterone.
- Differentiation of various milk ducts thanks to estrogen.
- More growth of the alveoli and additional differentiation thanks to prolactin and growth hormone (which also helps to regulate milk production).
- Oxytocin stimulates the milk ejection reflex (lactation).
- Additional breast growth — breast, nipple, and areola (the dark area around the nipples) — thanks to human placental lactogen.
- Other changes, such as higher insulin resistance and whatnot.
In doing the research regarding breasts and lactation and cancer risk, I did find ONE study that discusses lobule type and breast cancer risk: “Lobule Type and Subsequent Breast Cancer Risk: Results from the Nurses’ Health Studies”. This study used the questionnaires from over one hundred thousand nurses health stations and identified 1310 cases of people with benign breast disease (BBD) who developed breast cancer and 5273 controls.
Like I said in the past, I’m a layperson who’s studying for a BS in biochemistry, so while I did read the study in question to see whether the methodology is valid (and it seems like it is), I’m not as trained to read them as someone who has gotten their BS/Masters/PhD.
Anyways, what was their conclusion?
In this established nested case-control study of benign breast disease and breast cancer, women with predominant type 1 and no type 3 lobules had a reduction in breast cancer risk compared to women with all other lobule types, even after adjustment for histologic category of BBD. Some decrease in risk was observed for all categories of BBD, although the stratified analyses were limited by small numbers of cases and controls. These results suggest that having a larger proportion of type 1 lobules and no type 3 lobules may be protective against the development of breast cancer among women who have had BBD, regardless of their histologic category.
And how did they define the different types?
Type 1 lobules are the least developed and are present in the immature female breast prior to menarche, whereas type 3 lobules are the most fully developed and are usually seen in the breasts of women under hormonal stimulation or during pregnancy. Type 2 lobules evolve from type 1 lobules and are intermediate in their degree of differentiation. The breasts of nulliparous women are composed mainly of type 1 lobules, although occasional types 2 and 3 lobules are present; in contrast, type 3 lobules are the predominant structure in parous women. Type 4 lobules are present only during lactation and then regress back to type 3 lobules.
Long story short, they concluded that among women with benign breast disease, women who have more Type 1 lobules and less Type 3 (i.e. women who have never given birth) were less likely to develop breast cancer.
Uh oh. That’s contrary to the original article’s claim that women who have given birth are less likely to develop breast cancer thanks to more mature lobules. Strike 1?
There is evidence of permanent changes in the genes of Type 3 lobules which provide life-long cancer resistance.
Moving on to the next paragraph:
A premature delivery before 32 weeks doubles the risk of breast cancer because it leaves the breast with more places for cancer to start.
So far I’m only getting anti-choice sites, no source. That’s not a good sign.
On the other hand, I did find that Science Based Medicine did something regarding the abortion/breast cancer link; the conclusion was that there was absolutely no link. (The author of that article is a breast cancer surgeon and does research on breast cancer; he’s much more qualified than me to discuss this topic.)
Also, seriously, this makes NO sense. There’s no such thing as a cancer-proof cell. All cells can screw up and turn cancerous. You’re giving people who have been pregnant false hope.
And you’d think that with all of the differentiation going on, that there might be a even HIGHER chance of cancer. After all, the lobule is becoming more and more specialized. How would they be more cancer-resistant if they’re becoming more and more specialized?
Approximately 90% of miscarriages occur in the first trimester. However, the vast majority of natural miscarriages in the first trimester do not increase the risk of breast cancer. In these cases, pregnancy hormones are lower than those of a normal pregnancy due to either a fetal or an ovarian abnormality.
Wait, so my uterus can tell the future now?
Also, as the final nail to the coffin, the American Cancer Society weighed in. Guess what? They concluded that there is absolutely no link between breast cancer and abortion, both spontaneous and induced.
And, of course, if you’re curious, here are the ACTUAL risk-factors for breast cancer, because we need some reality and some actual legit science up in here.
Science: against fear mongering since <year>.
Tomorrow (if I have time for it): why adoption is not a substitute for abortion.