Girls born to mothers with high levels of BPA in their system during the first trimester of pregnancy weigh less at birth than babies with lower exposure, according to a new study.
The study adds to evidence that fetal exposure to the ubiquitous chemical bisphenol-A (BPA) may contribute to fetal developmental problems. Low birth weights are linked to a host of health problems later in life, such as obesity, diabetes, infertility and heart disease.
Researchers tested mothers’ blood during their first trimester and at delivery for BPA and also tested umbilical cord blood after delivery. The mothers-to-be were recruited at the University of Michigan Voigtlander Women’s Hospital in Ann Arbor, Michigan. They tested for both BPA and "conjugated BPA," the form BPA takes after the body processes it.
Bottom line: more BPA in woman’s blood meant babies weighed less. For every doubling in free, or unconjugated, BPA in the mothers’ first-term blood, babies weighed, on average, 6.5 ounces less. The research was published today in The Journal of Clinical Endocrinology & Metabolism.
Similarly, for every doubling of free-BPA in the woman’s blood at birth, babies weighed on average 3 ounces less.
“Having small babies at birth is a risk factor for a whole bunch of different things,” said Laura Vandenberg, an assistant professor of environmental health at the University of Massachusetts Amherst who was not involved in the study.
A study released this month out of China found BPA levels in mothers’ urine was linked to low birth weights. That study also found a much stronger association with baby girls.
Unfortunately for pregnant women, BPA—used to make polycarbonate plastic and found in some food cans and paper receipts—is found in most people.
The strong link between the first-term exposure and birth weights makes sense, said Vasantha Padmanabhan, senior author of the study and professor of pediatrics, obstetrics and gynecology, molecular and integrative physiology and environmental health sciences at the University of Michigan.
“When you think about development, early in the pregnancy is a critical time—when fetuses are most sensitive to insults such as stress, environmental chemicals. That’s why we looked at the first trimester,” she said.
About 8 percent of babies born in the United States suffer from low birth weights, considered less than 5.5 pounds, according to the U.S. Centers for Disease Control and Prevention. Other possible contributors to low birth weights include smoking or drinking alcohol during pregnancy, mothers’ lack of weight gain, mothers’ age and stress.
The University of Michigan study doesn’t prove BPA caused low birth weights. But it could play a role, as the chemical mimics hormones and can disrupt endocrine systems. Even though BPA clears from the body quickly, scientists suspect it could bind to receptors or could be stored in fat for release later.
Proper functioning of these receptors is critical to organ development and function.
The American Chemistry Council, which represents chemical manufacturers, said the study provides “no meaningful information on the safety of BPA.” The council has defended BPA as safe as used in food packaging.
Steve Hentges, a representative of the council, called into question using blood to measure BPA exposure. He also suggested BPA from another source contaminated the blood samples.
Padmanabhan said the study and BPA measurements “represent a true life scenario”, as blood was drawn with a researcher present to ensure no plastic contact.
The researchers did not find a link between BPA levels and baby boys’ weights. It’s not clear why the exposure was only linked to lower birth weights in girls, but the work suggests that females might be more susceptible to BPA exposure before birth.