The study, from the University of Michigan School of Public Health (SPA), found that women who deliver prematurely have three times as much phthalate present in their urine as mothers who reach full term.
Researchers from the SPA, including Professors John Meeker, Rita Loch-Caruso and Howard Hu, worked in collaboration with the National Institute of Public Health in Mexico and the US Centers for Disease Control (CDC). The group anaylsed data from a larger study by Hu, which followed 60 Mexican women during pre-natal visits at four clinics in Mexico City.
Higher phthalate levels
The study evaluated 30 women who delivered prematurely – defined in the research as less than 37 weeks - and 30 who carried to term. Urine samples collected during the third trimester were analysed and compared to the control group who did not deliver prematurely.
A statement from Meeker and his colleagues said they “found significantly higher phthalate metabolite levels in the women who delivered prematurely”.
“In a crude comparison prior to correcting for urinary dilution, geometric mean urinary concentrations were higher for the phthalate metabolites MBP, MBzP, mono-3-carboxylpropyl phthalate (MCPP), and four metabolites of di(2-ethylhexyl) phthalate (DEHP) among women who subsequently delivered preterm,” said the group. “These differences remained, but were somewhat lessened, after correction by specific gravity or creatinine.”
The SPA researchers said US premature births have increased by more than 30 per cent since 1981 and by 18 per cent since 1990. In 2004, premature births accounted for 12.8 per cent of live births nationwide. Meeker said premature birth was a significant risk factor for many childhood health problems that can continue into adulthood.
A couple of human studies have reported associations between phthalates and gestational age, but this is the first known study to look at the relationship between phthalates and premature births, he added.
"We looked at these commonly used compounds found in consumer products based on the growing amount of animal toxicity data and since national human data show that a large proportion of the population are unknowingly exposed," Meeker said. "One of the problems for consumers is that you don't know exactly which products contain phthalates because the products do not have to be labelled accordingly."
SPA said its research was a “stepping stone” to more detailed research in evaluating the role of phthalates in premature births. Researchers said they hoped to examine a larger population of pregnant women to corroborate these initial study findings.