HomeoldFour part series on the abortion-breast cancer link (ABC link)

Four part series on the abortion-breast cancer link (ABC link)

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“The abortion-breast cancer link (ABC link): Those stubborn facts again!

Part One of Four

The resurgence of the abortion-breast cancer debate—this time prompted by the introduction of bills in three states that would require warning women seeking abortion about the link between induced abortion and breast cancer—has again generated vicious and dishonest denials that any link exists. The worst example—but only one of many—was produced by Eric Zorn, writing in the Chicago Tribune.

In the face of Zorn’s malicious invective (he calls proposed “women’s right to know” acts now pending in New Hampshire, Kansas, and New Jersey “Activists’ Right to Lie to Women” acts), it’s a good time to set the record straight with accurate, scientific facts.

In this first of three articles on the ABC link, I’ll chronicle the history of epidemiological data going back over 50 years that shows a consistent statistical connection between a history of induced abortion and a higher incidence of breast cancer among women all over the world. I’ll also briefly talk about the curious logic used by deniers of the ABC link.

By way of background, abortion raises a woman’s risk for breast cancer in two ways; the debate is over the second, not the first. Scientists have long understood that the risk of breast cancer is reduced when a woman completes a full-term pregnancy. This “protective effect of childbearing” is lost with an abortion. The second way abortion increases the likelihood of breast cancer is that an abortion leaves a woman with more cancer-vulnerable breast tissue than she had before she became pregnant.

In 1957, a nation-wide study in Japan published in  the Japanese Journal of Cancer Research found that women who had breast cancer reported having had three times as many pregnancies end with an induced abortion. Of course, there were few studies in those days, as induced abortion was neither legal nor common in most of the world—and breast cancer was not that common either!

Most studies, in fact, did not distinguish between induced abortion and spontaneous abortion (what we usually refer to as miscarriage), a natural event that generally does not increase the risk of breast cancer. I will talk about the importance of this distinction in Parts Two and Three,

Then there were the results of a very prominent series of World Health Organization-sponsored studies in the late 1960′s. Led by a Harvard research team, the WHO study looked at women from four continents to find out whether early pregnancy reduces breast cancer risk. That turned out to be true for full-term pregnancies. But they also found that the results “were in the direction which suggested increased risk associated with  abortion — contrary  to  the reduction in risk associated with full-term births.”

The famous 1970 paper that summarized these WHO findings firmly established that full-term pregnancies confer protection against breast cancer. It has been unequivocal for over 40 years that a pregnant woman who chooses abortion will end up with a higher long-term risk of breast cancer than if she chooses instead to let nature take its course.

Every reasonable standard of informed consent requires a doctor to warn a patient of any adverse health consequences of having the intervention in question—abortion in this case—compared to not having the intervention. That alone defines a duty for abortion practitioners to inform their patients of the increase in future breast cancer risk.

But the ensuing four decades of research around the world, a world with an ever increasing number of women having had an induced abortion, have shown that it is even worse: Women who choose abortion are more likely to get breast cancer than if they had not gotten pregnant in the first place.

This trend, known among epidemiologists as the “independent risk” of abortion, has been the center of the controversy raging in the public square. Evidence of this independent risk of abortion first showed up among American women in a prominent study from USC published in 1981 in the British Journal of Cancer. Another dozen American studies showed the independent effect during the 1980′s and 90′s, as well as another dozen studies from Europe and Asia.

In 1996, along with colleagues from the Penn State Medical College, I published, in the British Medical Association’s epidemiology journal, a meta-analysis of all 23 studies then extant. Our paper proved that the average 30% increase in breast cancer risk among women who have had an induced abortion was “statistically significant”: in other words, this increase was more than 95% certain not to be due to chance. In the last five years, studies continue to emerge from nations where both abortion and breast cancer used to be rare–China, Iran, Turkey, Armenia—showing a clear and significant independent ABC link.

Yet strangely—and tragically—to all the world’s most prominent purveyors of public health information, from the U.S. National Cancer Institute, American Medical Association and the cancer charities such as the American Cancer Society and Komen, to Health Ministries around the world and the WHO itself, the ABC link does not exist!

And the argument upon which all the denials are based boils down to something called variously, “reporting bias” or “response bias.” It goes like this.

When a study population of women is interviewed to determine their reproductive history, the argument is that healthy women will be more reluctant to admit they had an abortion, whereas women with cancer are more likely to tell the truth about their abortion history.

If this is true, then studies which rely on interviews that look back in time (retrospective studies) will overestimate the association of induced abortion with breast cancer patients, compared to healthy women. Proponents of this hypothesis go on to claim that only a study based on medical records, or one which follows women prospectively in time– i.e., a study in which the abortions are recorded before anybody knows who will get breast cancer–can give accurate results.

As much of a stretch as the response bias hypothesis seems–flying in the face of a half-century’s worth of data from studies on women from all over the world conducted by long-standardized epidemiological methods–it is a testable hypothesis. In fact it has been tested again and again, and found wanting, but that has not muted the chorus of official denial of the ABC link.

That leads to part II of this series, in which we will segue from the ABC link as the focus of our inquiry, to the world-wide cover-up of the ABC link, and its now over 40-year-long trail of published evidence.

The abortion-breast cancer link (ABC link): Those stubborn facts again!

Part Two of Four

In Part I of this three-part series of articles on the link between abortion and breast cancer (the ABC link), I described the two primary ways in which abortion increases a woman’s future risk of breast cancer:

1. via loss of the protective effect of an otherwise full-term pregnancy, and

2. via the increase in cancer-vulnerable tissue produced by the pregnancy hormones, making women who choose abortion more likely to get breast cancer than if they had not gotten pregnant in the first place.

There is no debate about the former. Scientists have long understood that the risk of breast cancer is reduced when a woman completes a full-term pregnancy. This “protective effect of childbearing” is lost with an abortion.

The latter trend, known among epidemiologists as the “independent risk” of abortion, has been the center of the controversy raging in the public square. Hence, it has been the main area in which scientific evidence has been systematically covered up for some 40 years now. This cover-up is the subject of our inquiry in the present essay.

Evidence of this independent risk of abortion first showed up among American women in a prominent study from Malcolm Pike and colleagues at USC, published in 1981 in the British Journal of Cancer. They found an elevated risk of 140%, a result Pike himself would attempt to minimize years later.

The first study clearly aimed at covering up this result appeared in the same journal the following year. The 1982 study was conducted by the group led by Sir Richard Doll. Doll’s then impeccable reputation as Oxford’s top epidemiologist was enough to repress the red flags raised by Pike’s prominent study.

In their study, the Doll group claimed—right in the study’s abstract—that their “results are entirely reassuring, being, in fact, more compatible with protective effects (of abortion vis-à-vis breast cancer) than the reverse.” They also claimed a much larger and older study population than Pike’s—1,176 women aged 16-50, compared to only 163 women under age 33—implying a much more statistically reliable study.

Like all epidemiological studies, statistical tables full of numbers dominated the pages. But note, the actual number of women who had had an induced abortion was nowhere to be found; the lone descriptor was “only a handful.”

Hence, far from being “entirely reassuring” about the safety of abortion, the Doll study was in reality, entirely irrelevant. Almost all their data were derived from spontaneous abortion (miscarriage), a natural phenomenon which does not elevate breast cancer risk.

To this day, the conflation of spontaneous and induced abortion is used by health authorities worldwide to dilute the connection with induced abortion to render it insignificant. It is one of the major ways by which the ABC link is dismissed.

Not surprisingly, the successors of the very same group at Oxford constitute one of those prominent authorities. They have published at least five ABC-link cover-up studies. The most prominent principally authored by Valerie Beral, appeared in the prestigious journal The Lancet in 2004. (I wrote about this study at length in the May 2004 edition of National Right to Life News.)

Some background is needed to understand the central role of the 2004 Beral “reanalysis.” In 1996 my colleagues at Penn State Medical College and I published a “comprehensive review and meta-analysis” of the independent ABC. At that time, there were 23 extant published studies from around the world. Putting them all together revealed a statistically significant, 30% overall increased risk of breast cancer among women who had had any abortions.

By 2004, the number of published studies with ABC link data had risen to 41, but Beral’s Lancet “reanalysis” assembled data from 53 studies, many of them not previously published. One would think, logically, that Beral’s study comprised the 41 extant published studies and another 12 as yet unpublished ones.

In fact that would be way off the mark. Beral’s “reanalysis” was actually of 52 studies. Only 24 of them had been previously published while 28 studies (more than half) not previously published. Knowledge of the criteria for exclusion (of the previously published) and inclusion (of the previously unpublished) is crucial.

On what basis were 17 published studies excluded from the Beral “reanalysis”? Eleven were excluded for the following four dubious reasons:

“Principal investigators…could not be traced”

“original data could not be retrieved by the principal investigators”

“researchers declined to take part in the collaboration”

“principal investigators judged their own information on induced abortion to be unreliable” (even though it had been vetted by peer review and published in a prominent medical journal—and never retracted).

In addition another four previously published studies were simply never mentioned at all. Only two were excluded for legitimate scientific reasons.

The fact that the majority of the previously unpublished studies had not stood the test of peer review is troubling enough. But a closer look at the results of studies Beral et al. excluded is even more revealing.

Of the 41 previously published studies, 29 show increased risk of breast cancer among women who have chosen abortion. (Epidemiologists call this a “positive association.”)

Sixteen were “statistically significant,” which means there is at least a 95% certainty that the results cannot be explained by chance. But Beral excludes 10 of these for reasons that simply are not supportable.

If we average all of the 15 studies that Beral inappropriately excluded, they show an average breast cancer risk increase of 80% among women who had chosen abortion. By selectively eliminating studies that show an ABC link, Beral is able to find there is no significant effect of abortion on the risk of breast cancer.

Having thrown out studies that contradict her thesis, she then included studies that are plagued with serious deficiencies.

Beral divided them into two types: (1) those which used retrospective methods of data collection (i.e., interviews of breast cancer patients versus women who had not had breast cancer), and (2) those which used prospective methods (i.e., medical records taken long before breast cancer diagnosis).

Beral told the Washington Post at the time that retrospective data-based studies are thought to be less reliable. Women with breast cancer, she said, “are more likely than healthy women to reveal they had an abortion, leading to the conclusion that there are more abortions among this group.” This “reporting bias” or “response bias” is a key to Beral’s argument.

But something you’d never know is that this hypothesis has been disproved over and over again in studies as far flung as Japan, the United States, and Greece!

There is only one study that  claims direct evidence for such a reporting/response bias— a Swedish study, conducted by a group headed by Olav Meirik of the World Health Organization (WHO). They did so based on an assumption that breast cancer patients had “overreported” abortions (i.e., imagined abortions that had never taken place!).  However,  in 1998 the authors  publicly retracted that assumption!

Notwithstanding this retraction Beral and others who deny the ABC link  continue to cling to the original 1991 study as evidence of reporting bias! Meanwhile, other studies in the U.S. clearly showed no such bias in ABC link research.

In Part Three I will review the unseemly parade of about one fraudulent ABC link paper per year between 1997 and 2008. They issued from such prestigious institutions as Oxford (again and again!), Harvard and the Karolinska Institute in Sweden, where the Nobel Prizes come from.

All were based on prospective data, so they could be touted as superior in design and execution. But you won’t believe some of the garbage that passed as science, in a clear effort to convince the world that the ABC link is a fiction.

The “dagger under the table”–The Abortion-Breast Cancer link (ABC link)

Part Three of Four

In part II of this series of articles on the link between abortion and breast cancer, I described how the “reporting bias” or “response bias” argument has been systematically used by the most prominent medical research authorities in the western world to deny the reality of the ABC link. It is as hugely important to critics as it is demonstrable false. The argument goes as follows.

When you compare the reproductive histories of breast cancer patients to healthy women (“retrospective” data-based studies), the cancer patients will be more truthful about their past abortions than healthy women. If true, this would result in breast cancer falsely appearing to be more common among post-abortive than non-post-abortive women, thus incorrectly indicating an increased risk with abortion.

The argument continues, to prove whether there is a reporting bias that results in an ABC link, studies are needed which do not rely on women’s recall and reporting of their reproductive histories. Rather those studies which rely on medical records of abortion and/or which follow cohorts of women in time after their abortions, are sure to be free of possible of reporting bias. Epidemiologists refer to this latter type of data as prospective, i.e., data on abortion exposure are gathered before it is known who will end up being a breast cancer patient and who will not. Such studies as these, it is contended, are far superior to those which rely on retrospective data.

About a dozen prospective data-based studies emerged from some of the most high profile institutions and journals during the period 1997 to 2008. All of them showed no ABC link, fueling the official denial of the link far and wide, a wall of denial still essentially in place.

But, in fact, just because a study is based on prospective data, it is not necessarily scientifically sound. Those dozen studies are largely provably false. In Part Three, I provide a taste of what has passed for science in official circles–scientific merit being adjudged strictly according to whether a study supports the “safe abortion” narrative.

It is more than interesting that the first solid prospective data-based study had actually been published back in 1989. Based on fetal death certificates filed for abortions done in New York State, the study found the politically incorrect results that women who’d had an abortion nearly doubled their breast cancer risk. Since this does not fit the “safe abortion” narrative, the authors of the recent spate of prospective studies have systematically misrepresented the New York study. Some ignore it altogether, some mischaracterize it as being subject to reporting bias, and some flat-out claim no such study exists!

In 1997, a prospective study on Danish women (funded by the U.S. Department of Defense) was published in the top American medical journal, the New England Journal of Medicine and found  precisely zero effect of abortion on breast cancer risk. It’s timing is significant because that was exactly three months after my group’s “comprehensive review and meta-analysis” gained substantial media traction. We had found an overall increased breast cancer risk of 30% among post-abortive women worldwide.

The Danish study was widely touted as definitive because it was so big: based on 1.5 million women, representing an aggregate of over 370,000 abortions and over 10,000 cases of breast cancer.

But upon closer examination, the Danish study reads like a manual of how to distort the data in order to achieve a desired outcome. Among the more egregious examples was the use of breast cancer records dating back to 1968, but including abortions only from 1973 onwards. This is a violation of the most basic scientific rule: Cause must precede effect! But apparently, not when you are trying to prove abortion is safe for women.

Yet more effective at covering up the truth was the omission of legal abortion records dating back to 1940, when abortion was legalized in Denmark, and then writing  as if the date of legalization were in 1973.

Then there is the trick that has been used in most of the prospective studies purporting to show that there is no ABC link: Limiting the follow-up period after abortion. You see, one of the strengths of retrospective studies is that typically, older women are interviewed about their reproductive histories years or even decades after their abortions.

This is hugely important because it often takes 10-20 years for cancer to develop after an abortion. But in the 1997 Danish study, fully one fourth of the subjects were still under the age of 25 at the end of the study! Of course, these young women had lots of abortions, but almost no breast cancer.

But not only was this lack of follow-up time used as a device to eliminate the evidence of increased breast cancer risk with abortion in prospective study after study, a very diverse bag of tricks can also be found at work.

For example, one of the many ABC cover-up studies published by the Oxford group of epidemiologists, published in 2001, showed no ABC link. But the medical records they used had clearly missed over 90% of the abortions performed on women during the study period. Buried deep in the paper’s discussion section was the following curious revelation: “Our data on abortions are substantially incomplete…” That alone should have convinced the journal to discard the study on the spot!

Then there is the “dagger under the table” technique. The “dagger” is the printed dagger that signifies a footnote. There was a pivotal footnote that appeared under the key data table in the prestigious Harvard Nurses Study II, published in 2007.

The daggered footnote signifies, in that case, that a key statistical adjustment to the data on abortion was omitted from the overall result. Hence, the authors could (misleadingly) report no significant ABC link in the overall conclusion, rather than a significant risk increase of at least 10% that they had actually observed.

Finally, another key trick now used by just about all ABC-link deniers is the complete omission of cases of breast cancer in situ, the type of breast cancer which appears earliest, and the incidence of which type has also dramatically risen in the US by some 400% in recent decades!

At this point one may seriously ask: How on earth can the medical research establishment get away with such a widespread, systematic cover up of a serious health risk from an elective procedure? Of course there is the media complicity, but there is also the ability of a small cohort of well-placed individuals in key positions of agencies such as  the US National Cancer Institute (NCI), which funds most of the cancer research in the US. Scientists who don’t toe the party line can lose their research grants.

In the final installment of this series, I’ll describe the biology that underlies the ABC-link.

The Stubborn Biological Facts regarding the Abortion-Breast Cancer link (ABC link)

Part Four of Four

In the three previous installments of this series, I documented the epidemiological evidence for the abortion-breast cancer link (ABC link), and the ongoing wall of denial from the official purveyors of public health information, including the National Cancer Institute (NCI). In this final installment, I’ll go over the basic, underlying biology of how and why abortion interferes with normal breast development and breast health, thus leading to a higher risk of breast cancer later in life for women who have chosen abortion.

Everyone knows that a woman’s breasts, as part of the reproductive system, do not develop until puberty. But most people—even doctors—do not know that the breasts really do not develop substantially even at puberty: they essentially just grow in size. What that means is that from the time of puberty, a girl has a lot more breast tissue capable of growing—and capable of becoming cancerous—than she had before puberty. Thus does puberty open what breast cancer researchers call the “susceptibility window.”

The susceptibility window—when potentially cancer-causing mutations can collect in vulnerable breast lobule cells—only closes when a woman has her first full-term pregnancy. It is in fact at about 32 weeks of a normal pregnancy that most of the primitive, growing cells of the breast become differentiated into cells that can actually produce milk.

Why are these mature cells resistant to becoming cancerous? Because their ability to proliferate has been turned off. That explains not only the epidemiological evidence showing abortion’s link to future breast cancer risk, but also the fact that a live birth before 32 weeks gestation also increases risk; the effect on the mother of “terminating” a normal pregnancy  is the same, regardless of the fate of the child.

A little more detailed look at what happens to the breasts during pregnancy clearly shows two major ways in which abortion raises the risk of future breast cancer.

The future milk-producing structures in the breast that multiply during puberty are called Type 1 and Type 2 lobules. It is Type 1 and Type 2 lobules where almost all breast cancers start. Microscopically, these lobules look rather like trees in winter, with the branches bare except for small buds. After puberty but before first pregnancy, almost 100% of the lobules are Type 1 and 2—to emphasize again, where almost all breast cancers begin.

When a woman becomes pregnant, the hormones estrogen and progesterone surge and cause a massive growth spurt in the breasts, doubling the size of the lobular tissue by mid-pregnancy (20 weeks gestation). But by 32 weeks gestation, only about 20% of the lobules are still cancer-vulnerable Type 1 and 2. Most have matured to Type 4 and can produce colostrum (milk).

Putting all this together in terms of breast cancer risk, we can see that putting off childbirth until a woman is older results in a greater likelihood of getting breast cancer, because the susceptibility window is open much longer. This fact has been well established, ever since a definitive, international multi-center study commissioned by the World Health Organization (WHO) was published in 1970.

Moreover, it is widely known to be responsible for most of the difference between the high rate of breast cancer incidence among women in North America and Europe—who typically wait until they are in their late 20′s or 30′s to start having children—and the much lower cancer breast cancer incidence rates among women in Asia and Africa. Thus there is no controversy about the fact that the longer a woman waits to start having children, the higher her future risk of breast cancer. Importantly, by delaying the closing of the susceptibility window, abortion abrogates the protective effect of full-term pregnancy.

But abortion does more damage than merely postponing first childbirth, nullifying the protective impact that comes because immature and cancer-prone breast tissue have matured. The surging estrogen and progesterone of a normal pregnancy multiplies the number of Type 1 and 2 lobules. If the pregnancy is aborted, this creates more places for cancers to start, because the third trimester maturation to type 3 and 4 lobules never is allowed to happen.

That is why dozens of published epidemiological studies from around the world, starting as far back as 1957, continue to emerge which show increased breast cancer risk among women who have chosen abortion. This trend even showed up in the WHO report back in 1970, wherein the authors noted that their results “suggested increased risk associated with  abortion — contrary  to  the reduction in risk associated with full-term births.”

Finally, it should be noted that there are two more ways—indirect ways—in which abortion can increase a woman’s future breast cancer risk which often are overlooked.

First, abortion increases the risk of premature birth in subsequent pregnancies. Not only does this have devastating consequences in terms of increasing the incidence of such congenital disabilities as cerebral palsy and autism, but (as noted above) premature deliveries before 32 weeks gestation increases the risk of breast cancer, the same as later-term abortion does.

Second, it is also well established that breast feeding reduces the risk of future breast cancer, and breast feeding is of course not possible after the baby is aborted.

Clearly, nothing reduces the risk of future breast cancer like starting childbearing early. That’s a big reason why teenage and early 20-something mothers in particular should be advised against abortion. Young motherhood will drive their future breast cancer risk way down, while abortion will drive it way up. It really is as simple as that.

But what about abortion of subsequent pregnancies? Again, half a century’s worth of data confirms that the independent effect of abortion–above and beyond the effect of postponing first childbirth—is the same for abortion of any pregnancy. That would be about a 30% increased risk on average.

I suspect few women would be willing to take that risk, if only they knew about it.

Editor’s note. Joel Brind, Ph.D., is a professor of biology and endocrinology at Baruch College of the City University of New York, and  is co-founder of the Breast Cancer Prevention Institute.  He is a frequent contributor to NRL News and to NRL News Today.


Chelsea Garcia is a political writer with a special interest in international relations and social issues. Events surrounding the war in Ukraine and the war in Israel are a major focus for political journalists. But as a former local reporter, she is also interested in national politics.

Chelsea Garcia studied media, communication and political science in Texas, USA, and learned the journalistic trade during an internship at a daily newspaper. In addition to her political writing, she is pursuing a master's degree in multimedia and writing at Texas.

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