Wednesday, October 2, 2013

Does BPA Exposure Cause Miscarriages?

BPA, along with many other man-made chemicals, has become quite prevalent in our environment, and have been shown to possess estrogen-like characteristics which have led to significant health problems for humans and wildlife alike.  BPA, along with other similar endocrine disruptors, can be found in many different products, including the plastic in your water bottle, to the thermal paper for your printer, and even in your dental sealants.  As you can imagine, something so potentially damaging and yet so prevalent in our environment is great cause for concern.

BPA can interrupt or otherwise harm many different hormone-dependent systems in the human body, one of which is the reproductive system.  Other endocrine disruptors, such as dioxin and DDT, have been implicated as linked to some cancers, endometriosis, small birth weights, and pre-term births.  Since these are endocrine disruptors that are known to cause problems in the reproductive system, the next question becomes whether or not these man-made chemicals are somehow associated with miscarriage early on in pregnancy. 

How common are miscarriages?

Somewhere between 10 and 25% of all pregnancies will likely result in spontaneous abortions, i.e. miscarriages.  Between 40 and 70% of these miscarriages are associated with chromosome abnormalities, in particular aneuploidy (having too few or too many chromosomes).
Previous studies have shown that BPA exposure during oogenesis or spermatogenesis results in increased incidences of aneuploidy, so naturally, the most obvious question would be: is BPA associated with miscarriages? 

BPA à Aneuploidy; Aneuploidy à Miscarriage; BPA --?--> Miscarriage?

BPA has been found to be present in the urine of at least 90% of Americans.  In Japan, about 350,000 tons of BPA per year is produced for various plastic-based products.  Thus, as in the US, BPA is very common in Japan as well as other parts of the world, and where a group of researchers set out to determine if BPA is at any way associated with miscarriages in the population.

45 women with a history of 3 to 11 miscarriages were examined during this study, with 32 healthy non-pregnant and no history of infertility or miscarriage used as controls.  Serum BPA levels were measured for all women in the study, in addition to several antibodies, immune response cells, progesterone, and prolactin.

What did they find?

Results of the study found that BPA is highly associated with the history of miscarriage in Japanese women, particularly with those women that were ANA-positive (a.k.a. they have antinuclear antibodies present in their blood, which may or may not be a red flag for an immune response and has also been linked to recurrent miscarriages). 

While this was not a study to get at the question of HOW BPA can cause miscarriage, however it does provide evidence that BPA exposure is associated with recurrent miscarriage and deserves further research.

Why are these pregnancies aborted?  Does BPA increase aneuploidy in eggs or sperm?  Does BPA interfere with early embryonic development in another manner?  More research will certainly give us the answer, and as luck would have it, that research has been done!  Stay tuned….

Source: Sugiura-Ogasawara, M., Ozaki, Y., Sonta, S., Makino, T., and Suzumori, K. 2005. Exposure to bisphenol A is associated with recurrentmiscarriageHuman Reproduction 20(8):2325-2329.

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