Chemicals called phthalates, found in
plastics and cosmetics, may be linked to a raised risk of babies being born prematurely, a new study suggests. Researchers found that women who delivered babies
before 37 weeks gestation had higher levels of phthalates in their urine,
compared to women who delivered their children at full term, which is 39 weeks.
"Preterm birth is a real public health
problem," said John Meeker, who led the study. "We're not really sure
how to go about preventing it, but this may shed light on environmental factors about which people may want to be informed."
Meeker, from the University of
Michigan School of Public Health in Ann Arbor, added, "We knew that
exposure to phthalates was extremely widespread in the US and possibly
worldwide, and preterm births increased for unknown reasons over the past several
Phthalates are included in products
for a variety of reasons, including to make plastic flexible. Past studies have also found evidence that would suggest the chemicals may be tied to earlier births. Previous research has linked the chemicals to shorter pregnancies
and lower birth weight.
"There are many possible routes of
exposure depending on the chemical and the scenario," Meeker
said. Most commonly, the chemical enters the body through food and beverages.
It may also be absorbed through the skin. For the new study, the researchers
used data from a study conducted at Brigham and Women's Hospital in Boston
between 2006 and 2008.
Surveys and samples
During the study, pregnant women were asked
to fill out surveys and provide urine samples throughout their pregnancies. The
researchers compared 130 mothers who delivered their babies before 37 weeks to
352 women who delivered their babies at term. While each woman provided
numerous urine samples during her pregnancy, the researchers analysed three
to measure the amount of phthalates in their bodies.
They looked for breakdown products of a
phthalate chemical known as DEHP. Overall, the two by-products MEHP and MECPP
were more abundant in women who delivered their children early, compared to
women who delivered after 37 weeks.
That was also true for MBP, a by-product of
Dibutyk phthalate. According to the US Environmental Protection Agency, those
chemicals are used to make products – such as plastic pipes, shower curtains
and food packaging – soft and flexible. Each of the phthalates examined was
linked to a risk increase of anywhere from 16% to 65% increase in risk for
It adds up
About one of every eight infants is born
prematurely in the US, according to the Centres for Disease Control and Prevention.
Shanna Swan, who wrote an editorial accompanying the new study in JAMA Paediatrics,
said that difference may not mean much to an individual woman, but it adds up
across a large population. Swan is a professor Department of Preventive
Medicine at the Icahn School of Medicine at Mount Sinai in New York.
"There are a lot of indications or
warnings that signal that women avoid phthalates when they can," she said.
"I say 'when they can' because it's difficult. Most of the
exposures are silent and we are not aware of them," she added. "We
don't know how to avoid them. Previous studies have suggested that people
who use fresh and organic produce – such as certain religious groups – have
lower phthalate levels," Swan said. She added, however, that not many
studies have examined the relationship between phthalates and preterm births.
Levels can change
Some studies, according to the researchers,
have found no negative side effects from phthalate levels, but those only used
levels from one urine sample. Phthalate levels can change during pregnancy.
Meeker said the new study can't prove higher
phthalate levels caused women to deliver early or if they should stay away from
the chemicals. "Our study wasn't really geared to look at that," he
said. "Women may want to limit exposure if they can, but there are so many
different points of exposure, which makes it difficult."