|Sugiura-Ogasawara, M, Y Ozaki, S Sonta, T Makino and Kaoru Suzumori 2005. Exposure to bisphenol A is associated with recurrent miscarriage. Human Reproduction 20:2325-2329.
In 2003, Hunt et al. reported that bisphenol A causes meiotic aneuploidy in mice. This report stimulated concern and speculation about its relevance to humans, because meiotic aneuploidy is the largest known cause of spontaneous miscarriage in people and because human exposure to bisphenol A is so widespread, thanks to its use in consumer products. The exposure level sufficient to cause the effect in mice was within the range people experience in the general population.
Bisphenol A in the news
With this study, Sugiura- Ogasawara et al. provide the first, indication that BPA is associated with recurrent miscarriage in people, as predicted by Hunt et al.'s results. They found higher levels of BPA in women with a history of recurrent miscarriage, and evidence of meiotic aneuploidy in their miscarried fetuses.
This is the second study to be published within a month to test the impacts of endocrine disrupting chemicals in people based on animal studies. Just two weeks ago, Swan et al. showed a highly significant relationship between elevated phthalate levels and genital abnormalities in boys, as predicted by work on rodents.
Skeptics of human impacts of EDCs have repeatedly claimed that 'we have decades of experience with X or Y and there is no evidence of harm in people.' The flaw in that argument is that the relevant human studies haven't been done; they are confusing absence of data with proof of safety. Now that epidemiologists are using animal data to guide their research, we have direct contradictions of those assertions.
What did they do? In their prospective study, Sugiura- Ogasawara et al. compared BPA levels in the serum of 45 women with a history of recurrent miscarriage to serum levels in 32 pregnant women with histories of successful pregnancies. They tracked the women through their next pregnancy to see whether it was successful. They also examined the miscarried fetuses of unsuccessful pregnancies for evidence of chromosomal damage consistent with aneuploidy. In addition, they examined the women for several immune system parameters and thyroid levels.
What did they find? Bisphenol A levels were more than three times higher in women with a history of recurrent miscarriage (2.59 ng/mL vs. 0.77 ng/mL). This difference was statistically significant (p = 0.024).
Among the women with previous miscarriage, 17 miscarried once again in the pregnancy being tracked by Sugiura-Ogasawara et al. Their BPA levels tended to be higher than those who successfully completed their pregnancy, although this difference was not statistically significant: 4.39 ng/mL vs 1.22 ng/mL.
Of the 13 miscarried fetuses whose tissue was available for analysis, 4 were aneuploid: each had one excess chromosome. The BPA levels of their mothers averaged 12.5 ng/ML.
While there was no difference between case and control mothers in thyroid status, cases showed higher levels of antinuclear antibodies, an indication of immune system problems.
What does it mean? This is a preliminary study with a small sample size. Despite the small sample, the fact that Sugiura- Ogasawara et al. found a significantly higher BPA levels in mothers experiencing recurrent miscarriage is a worrisome tentative confirmation of predictions from animal studies. Clearly this work requires replication with a much larger sample size. But the fact that this is a predicted result based on solid animal research increases its plausibility even with a small sample.
It is nonetheless now inappropriate for skeptics to assert there is no evidence of harm. And the fact that this is a predicted result based on solid animal research increases its plausibility.
According the authors, in people in general "about 40–70% of sporadic spontaneous abortions appear to be caused by chromosomal abnormalities of the conceptus,and aneuploidy is especially important," with abnormal embryonal karyotypes found in 10–50% of recurrent miscarriage cases. The possibility that BPA may be a cause of some percentage of these abortions opens the possibility that some cases of spontaneous abortion may be preventable through exposure reduction.