Are plastic chemicals in dads hurting embryos?

Turns out, moms, it's not just about you staying off alcohol and avoiding potentially harmful chemicals while pregnant or trying to become so. Your partners' exposure to plastics and packaging could play an important role in your ability to conceive a child.

Senior author Richard Pilsner (Credit: Umass.edu)

A father’s exposure to chemicals commonly found in plastics, personal care products and food packaging might decrease the quality of embryos produced by their sperm, according to a new study out of Massachusetts.

The study, published today in the journal Human Reproduction, is the first to examine dads’ exposure to phthalates and embryo quality through five days of in vitro fertilization (IVF). The lower quality embryos had fewer signs of the type of progress that leads to a fetus.

The findings suggest men’s exposure to the chemicals—used in vinyl products, food packaging, fragrances and in other plastics to make them pliable—might hamper the development of their unborn.

Embryos are the result of a fertilized egg in a woman and are the precursor to the fetus. About 12 weeks into pregnancies, the unborn is considered a fetus.

Most people have phthalates in their bodies and the compounds disrupt the endocrine system—interfering with hormones that are crucial for reproduction.

While the study doesn’t prove phthalates in men lead to poor quality embryos, it adds to mounting evidence that the ubiquitous chemicals may impact pregnancies.

“Sperm mature over 72 days average, almost three months,” said senior author of the study, Richard Pilsner, an epidemiologist and assistant professor at the University of Massachusetts Amherst. “During that time, we may tell men to maybe try to avoid phthalates. There’s no way to totally escape exposure but you could minimize it.”

Led by Pilsner, researchers collected 761 immature eggs from 50 couples undergoing IVF at the Baystate Medical Center in Springfield, Mass., and checked their progression to embryos. They tested embryos at three days and five days after the eggs were fertilized, and collected urine samples from the couples on the same day as the semen sample and egg retrieval to test for phthalate metabolites, substances formed after the body processes phthalates.

At day five, high exposure to phthalates in men was linked to fewer—or no—signs of the type of development that eventually leads to a fetus and placenta compared to men with lower exposure.

Phthalate exposure for fetuses has been linked to genital defects, lower IQs and miscarriages but it’s not clear what impacts this poor embryo quality could mean for the unborn. Russ Hauser, a professor of reproductive physiology at Harvard University, said in an email that the impacts might range from pregnancy loss to effects on children's health later in their life.

"Sperm mature over 72 days average, almost three months. During that time, we may tell men to maybe try to avoid phthalates."-Richard Pilsner, UMass Amherst Shanna Swan, a professor of reproductive science at Mount Sinai Hospital in New York who was not involved in the study, said the study is limited in that it is small, and not representative of the general population because it only included couples undergoing IVF.

“People that go through assisted reproduction have access to medical care, they have to have enough money to do it … in a lot of ways they’re not representative [of the general population],” she said.

The authors didn’t see the same link at day three, which, they say, could be because any molecular changes due to phthalates at that time could be too subtle to tease out.

They also didn’t see any association with the women’s exposure and decreased embryo quality. But this isn’t the first study to report a male-only effect. Higher phthalates in father’s urine was associated with an increased time for couples to conceive, according to a 2014 study.

Swan said the current study was strengthened in that it is “remarkably consistent” with the 2014 study. Some of phthalate metabolites linked to impacts in both studies are known to target male reproductive hormones, she said.

Pilsner said the next step is to follow the couples and see if there were any impacts from the reduced embryo quality, such as a decrease in successful births.

While that work is yet to be completed “starting life in best possible manner gives you a better chance of surviving,” he said.