BPA in Pregnancy Tied to Lower Weight in Girls

Can exposure to BPA early on in pregnancy affect your child? Yes, according to a new study, if your baby is a certain sex. Here's how to avoid the plastic product.

BPA in Pregnancy Tied to Lower Weight in Girls Maria Evseyeva/Shutterstock

Bisphenol-A (BPA) has become something of a toxic buzzword of late. It's everywhere you look—from the plastic that wraps your food to your long scroll-of-a-receipt at the drug store—and it can be particularly important to avoid during pregnancy.

But there may be more reason to steer clear of the plastic product while pregnant if you're hoping for a girl. Turns out, according to a recent study, mothers with higher levels of BPA in their system early on in pregnancy gave birth to girls with lower birth weights. More specifically: For every twofold increase in BPA in a mother during the first trimester, the weight went down about 6.5 ounces. As for the boys? There was no effect on their birth weights no matter if their mothers were exposed to BPA or not.

The findings come from researchers at the University of Michigan in Ann Arbor who took blood samples from 61 pregnant women early in their first trimesters and later from umbilical cords during delivery to learn more about how BPA affects children when exposed very early on in fetal development.

What is BPA?

BPA is a toxic chemical mostly used to create plastic-based products and resins like those found on the inside of canned foods. It's especially toxic for babies as its can affect hormones like estrogen, testosterone and insulin, possibly leading to gestational and developmental problems down the line. In this case, researchers primarily wanted to measure BPA levels early on in pregnancy rather than relying on blood taken from the umbilical cord after birth.

"When you are thinking about fetal development during pregnancy, the early period is very critical, when most of the organs are differentiating," senior author Vasantha Padmanabhan, a professor of pediatrics and obstetrics and gynecology at the University of Michigan Medical School, wrote in the study. "We felt if any chemical is going to have an impact, that would be the time point when you should look at associations."

And while yes, this study seemed to find an association between BPA levels and female birth weight, Padmanabhan is quick to point out that their small-scale study doesn't definitively mean exposure to BPA will lead to low birth weights.

The million dollar question

"I wish we had a simple answer," Padmanabhan tells Fit Pregnancy of why only female babies had lower birth weights when exposed to BPA. "During fetal development, there are several sex-specific hormonal changes that occur. For instance male fetuses see an early rise in testosterone, which female fetuses do not."

Males and females also react different to changing hormonal statuses in the womb, she adds, but "it is hard to pin-point out how BPA might lead to this sex-specific effect."

Though much more research is needed to have a definitive answer, it's still a good idea to avoid BPA as much as you can during pregnancy. Skip eating out as much as possible—since you don't know where they store their food—and use fresh ingredients, or those that comes in BPA-free cans. Also, eat out of (and store food in) a glass or ceramic container as much as possible, since BPA can take up residence in food when it's stored in plastic containers. Thermal paper—used for store receipts—also contains BPA, so avoid excessive overhandling.

Most of all, just use common sense and don't drive yourself crazy trying to rid your life of any and all traces of BPA—it's just not possible. Though this study might sound scary, the U.S. Food and Drug Administration said in a 2014 study that they "have not found any information in the evaluated studies" and still classifies BPA as safe for human exposure.