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Study Roundup: Pregnant? You May Want to Avoid BPA-Containing Products

New research shows that BPA could affect thyroid hormone levels in pregnant women and newborn boys

- by Alexia Severson

The Gist

thyroid scanningBPA (Bisphenol A), a chemical used in the manufacturing of plastic food containers, such as baby bottles, reusable cups and the lining of metal food and beverage cans, has been found to affect normal thyroid hormone levels in pregnant women and newborn boys, according to a new study by researchers at the University of California, Berkeley.

Normal thyroid function plays an essential role in pre- and postnatal growth and brain development in humans. While severe thyroid insufficiency in pregnant women and newborns has been known to alter cognition, behavior, and growth for more than a century, recent evidence suggests that mild alterations in thyroid function may also play a part.

BPA remains a controversial subject in the U.S. and recent studies have linked the chemical to other negative effects in human development, including an increased risk of miscarriages and birth defects.

 In July the U.S. Food and Drug Administration officially banned the chemical in baby bottles and sippy cups and many manufacturers of baby formula voluntarily removed the chemical from their packaging, but the American Chemistry Council maintains that the chemical is safe.

Learn more about where BPA can be found and how you can avoid it.

The Expert Take

This new study, published in Environmental Health Perspectives, investigates relations between exposure to BPA and thyroid function in pregnant women and newborns. To do this, researchers analyzed BPA levels in the urine samples of 335 women during the second half of pregnancy, and thyroid hormone levels in blood samples taken from the mothers during pregnancy and from the newborns within a few days of birth.

In mothers during pregnancy, for each doubling of BPA levels, there was an associated decrease of .13 micrograms per deciliter of total thyroxine (T4), a hormone produced by the thyroid gland that regulates growth and metabolism. In newborn boys, there was an associated 9.9 percent decrease found in thyroid stimulating hormone (TSH). Curiously, there was no association found among newborn girls.

While the results do not show a significantly large decrease in thyroid hormone level, Jonathan Chevrier, study lead author and research epidemiologist at UC Berkeley’s Center for Environmental Research and Children’s Health, said it is important to consider the impact of these results at a population level.

“We get concerned about a shift in the distribution that would affect those on the borderline," he said. "In addition, studies suggest that small changes in thyroid level, even if they're within normal limits, may still have a cognitive effect."

The Takeaway

While the American Chemistry Council, an association that represents plastics manufacturers, says BPA poses no risk to human health, the National Toxicology Program at the Department of Health and Human Services says it has "some concern" about the possible health effects of BPA on the brain, behavior and prostate gland of fetuses, infants and children.

Here are a few steps, provided by Mayo Clinic, you can take to minimize your exposure to BPA:

  • Seek out BPA-free products. Most aluminum cans or bottles have linings that contain BPA, while steel bottles or cans don't. Polycarbonate plastic is generally hard, clear, lightweight plastic. It often has the No. 7 recycling symbol on the bottom.
  •  Microwave with caution. Plastics can break down over time and may cause BPA to leach into food.
  •  Wash safely. The National Toxicology Program advises against washing polycarbonate plastics in the dishwasher using harsh detergents, although the American Chemistry Council says this is safe.
  •  Use alternatives. Glass, porcelain or stainless steel containers for hot foods and liquids instead of plastic containers.
  •  Cut back on cans. Many cans are lined with BPA-containing resin.

Source and Method

This study was published in Environmental Health Perspectives on Oct. 4.

Chevrier and his colleagues measured BPA concentration in urine samples collected during the first and second half of pregnancy in 476 women participating in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study. They also measured free thyroxine (T4), total T4 and thyroid-stimulating hormone (TSH) during pregnancy and TSH in newborns.

Women were excluded from the study if they had twins, had a miscarriage or stillborn baby, were lost to follow up, were taking medication that could affect TH levels or did not have a BPA urine measurement during pregnancy. TH was not measured in 169 mothers due to insufficient serum volume, leaving a final sample of 335 for the maternal analyses.

Other Research

It is not clear why no association between BPA levels and newborn girls was found, but animal studies have shown that BPA can affect males and females differently in both brain development and behavior.

For example, one study in newborn rats found a similar hyperthyroidic effect in males, but not females, while another study found that female rats had higher levels of an enzyme important in metabolizing BPA when compared with their male counterparts. It is yet to be seen whether that same relationship holds true for humans.

BPA has also been linked to miscarriages and birth defects in primates, in a recent study published in Proceedings of the National Academy of Sciences.

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