High levels of phthalates linked to preterm births: study

They've been linked with increased risk of diabetes, cancer and obesity. And now a new study is linking the commonly used class of chemicals known as phthalates with preterm birth.

According to the study from the University of Michigan School of Public Health and Brigham and Women's Hospital in Boston, women with the highest levels of exposure to phthalates — a group of man-made endocrine-disrupting chemicals often used in personal care products like perfumes, deodorants and lotions, as well as in plastic shower curtains and packaged foods — had two-to-five times the odds of delivering preterm than women with the lowest levels of exposure.

The findings were published online in the journal JAMA Pediatrics.

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Of the 482 women selected for the study, the 130 who gave birth prior to the 37-week mark showed significantly higher concentrations of four of the nine specific phthalate metabolites that were measured by researchers.

Of the 57 women in that group who had a "spontaneous preterm delivery," meaning there was no preexisting medical condition to explain the early birth, the link appeared even stronger.

There's still one unanswered question, however: Why?

"We have some ideas on how phthalates could cause preterm birth, although the exact mechanism is still unknown," says Kelly Ferguson, doctoral student at the U-M School of Public Health and first author of the paper. "One possibility we are considering is that phthalates are causing changes in oxidative stress or inflammation in the mother, and that these changes are leading to early labor."

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Dr. Thomas McElrath, a physician-scientist and key co-investigator on the study, reassures women that the findings shouldn't alarm them — yet.

"This is by no means the cause of premature birth, but it is a possible contributor— which is important because it is potentially modifiable," McElrath says. "This finding may be dramatic but women should not be alarmed. This is only the first step in a long research process that will be needed to clarify and confirm these results. It is simply too early to suggest making changes in prenatal care based on this study."

Current studies remain inconclusive in determining whether avoiding certain personal care products or eating foods with less packaging and processing would lower these levels.

The phthalate study came out of a desire to explore a growing health concern: the rise in rates of preterm births. Each year, 15 million babies are born before 37 weeks worldwide.

So far, health professionals have amassed a list of risk factors for giving birth early.

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A Canadian study published earlier this year listed several other risk factors for preterm births (PTB): a previous medical condition or developing a new one during pregnancy, expecting for the first time, or having had a previous preterm birth, miscarriage, or abortion. A woman with an education less than high school was also at greater risk of giving birth early.

According to the Mayo Clinic, in vitro fertilization, expecting twins or other multiples, an interval of less than six months between pregnancies and unusual uterus shape can also increase the risk of preterm births.

Certain lifestyle factors can also up the risk. Smoking, drinking, being underweight or overweight before pregnancy, high levels of stress, poor nutrition, lack of social support or prenatal care and working long hours on your feet can all contribute to preterm birth risk.

And a 2012 study found that women who were born premature are also more likely to have complications during their own pregnancies.

Dr. Anne Monique Nuyt, a neonatologist and researcher at Sainte-Justine University Hospital, encourages women that studies shouldn't scare them off from starting their family:

"Certainly people should not be afraid of starting their family and of being pregnant. I think like anything else, being informed — and therefore in turn making sure the health professional that's taking care of you is also informed — is simply the key."