An old ad for DES, a sythetic hormone that was later found to cause cancer in the daughters of the women who took it during pregnancy.

When I was in medical school, the nickname we had for them was “fireballs of the Eucharist.” That’s what it sounds like when you say “fibroids of the uterus” over and over again. Sort of.

Fibroids may indeed feel like fireballs to the women who suffer from them, and gynecologists see a lot of them. A recent ultrasound study found fibroids in over 80 percent of black women and 70 percent of white women. Back in 1992, a study based on post-mortem findings estimated that 50 percent of women had fibroids.

The uterus is a unique muscular organ whose cells have the capacity to grow rapidly during pregnancy and shrink back down to pre-baby size in just six weeks after delivery. A fibroid tumor is the result of unbridled growth of a single narcissistic muscle cell in the uterus — one that screams, “Look at me!” and refuses to stop growing.

In some women fibroids cause mild discomfort. But for the women who are plagued by them, they are excruciating, causing pain, excessive bleeding and in some cases infertility. Fibroids are the most common reason that women have hysterectomies.

About half of women with fibroids will not have significant problems from them. The other half will battle them with medications or medical procedures, a process that contributes to the high cost of health care for these women, loss of productivity and a diminished quality of life.

Just what causes these parasitic growths, first described in traditional Chinese medicine in 100 B.C. and in Western medicine in 1793, in London? All we have are associations. Genetic factors obviously play a role, since fibroids run in some families. Women who begin menstruating early are more likely to have them. So are women who are overweight. So are women who were born poor, and women born to diabetic mothers.

Exercise and eating a more plant-based diet may be protective against fibroids, but women who were fed soy formula during infancy are also more likely to have them. Interestingly, women who smoke are less likely to have them, but don’t use that as an excuse to start.

To a scientist who studies the links between reproductive health and our environment, findings in animals can be warnings for humans. The most intriguing connections are between fibroids and exposure to estrogenic chemicals. Baltic seals exposed to chemicals that mimic estrogen have been found to have fibroids.

Fibroids are also seen in lab rodents exposed to diethylstilbestrol (DES). Remember DES, the synthetic estrogen given to approximately 6 million pregnant American women between 1940 and 1970 in the belief that it would prevent miscarriage? It fell out of favor after a 1971 study showed that it caused rare vaginal cancers in the daughters of women who had taken it while pregnant, but it is also linked to uterine fibroids.

During the three decades when DES was used, it was given to more than just pregnant women worried about miscarriage. It was also placed in prenatal vitamins for good measure, so countless women were exposed. It was given to pregnant cattle as a way of improving the livestock industry’s bottom line. Odds are good that almost every child born in America in those three decades was exposed to varying levels of DES in utero. Could that be a reason why fibroids are so common in the women around us?

It will be a long time before we get the chance to find out. The effects of chemicals can cross generations. Your grandmother’s chemical exposures may determine your eventual health challenges. American cattle aren’t dosed with DES anymore, but many herds are still given synthetic estrogen, as well as testosterone, progesterone and growth hormone. By the way, DES is a kissing cousin to bisphenol–A (BPA), an estrogen-mimicking chemical that has become ubiquitous in our environment.

Because there are more than 80,000 chemicals in the marketplace that are poorly evaluated for human safety and weakly regulated by the U.S. Environmental Protection Agency, all of us will continue to be exposed, often in ways that make it difficult to trace the problem (like fibroids) to the cause.

The good news is that Senator Frank Lautenberg (D-NJ) has just reintroduced a bill to amend the Toxic Substances Control Act (TSCA) to give the EPA greater authority to obtain health and environmental data from chemical companies. This would help determine which chemicals could use further testing and, perhaps, which need to be removed from the marketplace to protect public health. It also demands that Americans have greater access to information about the potential dangers of the chemicals they work with on the job. It’s a law worth fighting for. With information like this we can begin to go beyond association and look for a cause.
Those interested in updates on Lautenberg’s bill can follow it at

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Post Doctoral Fellow at UCSF Program on Reproductive Health and the Environment

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