Kate Johnson

October 18, 2016

SALT LAKE CITY — Paternal exposure to phthalates before conception might be more harmful to the baby than maternal exposure, researchers have shown in the first study of its kind.

"Up until recently, paternal environmental exposure has been a largely unexplored determinant of offspring health," said Carmen Messerlian, PhD, from the Harvard T.H. Chan School of Public Health in Boston.

But she and her team found that paternal — not maternal — preconception urinary concentrations of di-(2-ethylhexyl) phthalate (DEHP) metabolites were associated with significant decreases in birth weight.

"For every log-unit increase in DEHP concentration, birth weight decreased by 113 g (P = .01)," she reported during a prize paper presentation here at the American Society for Reproductive Medicine 2016 Scientific Congress.

The researchers analyzed 178 singleton births from couples who underwent in vitro fertilization at the Massachusetts General Hospital Fertility Center from 2005 to 2015.

Environment and Reproductive Health Study

As part of the prospective Environment and Reproductive Health study, urine samples from the couples were analyzed for 11 individual phthalate metabolites.

Both men and women provided a sample on study entry, the women provided up to two additional preconception samples per treatment cycle and pregnancy samples at each trimester, and the men provided a preconception sample at the time of egg retrieval.

The average birth weight of the babies born was 3400 g, and "about 3% were below 2500 g, which is slightly less than the national average," reported Dr Messerlian.

There was a significant association between decreased birth weight and preconception phthalate exposure of the fathers, but not preconception or prenatal exposure of the mothers.

"Although maternal prenatal exposure was associated with a significant decrease in birth weight in the covariate adjusted models, this association became nonsignificant after adjustment for paternal preconception DEHP concentrations," she explained.

This research "acknowledges that conception is a couple-dependent reproductive process, and that both maternal and paternal exposures could affect fetal growth and ultimately fetal birth weight," said Melissa Smarr, PhD, from the National Institute of Child Health and Human Development.

Because of differences in study design and population, "we can't compare specific results," Dr Smarr told Medscape Medical News.

However, she said, the results presented "corroborate our research in the LIFE Study, which involved a general population for whom urinary parental preconception concentrations of some, but not all, DEHP metabolites were associated with lower birth weight" (Environ Health. 2015;14:73).

Dr Messerlian and Dr Smarr have disclosed no relevant financial relationships.

American Society for Reproductive Medicine (ASRM) 2016 Scientific Congress: Abstract O-1. Presented October 17, 2016.

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