Flame-retardant chemicals may increase risk of preterm birth, higher birth weight

Pregnant women exposed to specific classes of flame-retardant chemicals may face an increased risk of preterm birth, especially for baby girls, or higher birth weights, according to a Rutgers Health researcher.

Emily Barrett, professor and vice chair of the Department of Biostatistics and Epidemiology at the Rutgers School of Public Health and a member of the Rutgers Environmental and Occupational Health Sciences Institute, took part in a study that was published in Environmental Health Perspectives and funded by the Environmental influences on Child Health Outcomes (ECHO) Program at the National Institutes of Health.

Manufacturers commonly use organophosphate esters (OPEs) in products such as furniture, baby items, electronics, clothes and building materials to prevent fires and make plastics more flexible. People can come into contact with OPEs in various ways, including swallowing or breathing indoor dust or absorbing it through the skin.

In the past decade, OPEs increasingly have been used as flame retardants after polybrominated diphenyl ether (PBDE) flame retardants were phased out because of health risks. ECHO researchers wanted to learn how these now more widespread OPE chemicals might affect pregnancy outcomes such as preterm birth and birth weight.

“This is another regrettable case where new chemicals were introduced into consumer products without really understanding their health impacts,” said Barrett, a coauthor of the study. “Knowing now that OPE exposure is associated with adverse birth outcomes, we have to ask ourselves, ‘What are the downstream impacts on children’s health?’”

ECHO researchers found more than 85% of the study participants had three specific markers of OPE exposure in their bodies. Those three substances – diphenyl phosphate (DPHP), a combination of dibutyl phosphate and di-isobutyl phosphate (DBUP/DIBP) and bis(1,3-dichloro-2-propyl) phosphate – were associated with shorter pregnancies and higher risks of preterm birth only among female infants. Among male infants, higher concentrations of DPHP were associated with longer pregnancies.

Babies born to mothers with detectable levels of three other OPE markers – bis(1-chloro-2-propyl) phosphate, bis(2-methylphenyl) phosphate, and dipropyl phosphate – tended to have higher birth weights compared with those whose mothers had no detectable levels of these substances. Babies with a higher birth weight might be more likely to have jaundice, breathing problems or congenital disorders.

Researchers measured a total of nine OPE markers in urine samples collected from 6,646 pregnant participants across 16 ECHO Cohort Study Sites, often during their third or second trimesters. The researchers assessed birth outcomes, including the length of pregnancy and birth weight, using medical records or parent reports.

“These substances tend to stay in the body for short periods, usually just hours to days,” said Deborah Bennett at the University of California, Davis, who led the study. “Conducting more thorough studies with various urine tests can help us figure out how they might be linked to birth outcomes.”