The findings, presented today at the Endocrine Society’s 97th annual meeting in San Diego and funded by the National Institute of Environmental Health Sciences,
focus on the role of the placenta in responding to these chemicals and
altering levels of a key pregnancy hormone. These results suggest that
there may be reason to push routine clinical testing earlier in
pregnancy to check for the effects of chemicals and help guide potential
interventions to protect the health of the baby.
“Phthalates are pervasive,” said Jennifer Adibi, M.P.H., Sc.D., assistant professor of epidemiology
at Pitt Public Health. “Reducing exposure to phthalates and other
hormone-disrupting chemicals is something that needs to be addressed at a
societal level through consumer advocacy and regulation, and education
of health care providers.”
The research builds on a study led by Shanna S. Swan, Ph.D., of the Icahn School of Medicine at Mount Sinai that was published in February in the journal Human Reproduction.
Dr. Swan is senior investigator on this presentation, which provides
new information about how phthalates target a key pregnancy hormone
called human chorionic gonadotropin (hCG), which is made by the placenta
and can be measured in the mother’s blood and urine.
“The placenta, which is an extension of the fetus and a target of
the chemicals in our bodies, broadcasts information early in pregnancy,
through hCG, about what might be occurring to the fetus from chemical
exposure,” said Dr. Adibi. “A long-term benefit of this research might
be the development of new knowledge and methods for earlier screening in
pregnancy, with the potential to act on this information to improve the
long-term health of the future child.”
Dr. Adibi and her colleagues analyzed data collected from
approximately 350 women and their babies who participated in a
multicenter investigation called The Infant Development and the Environment Study
(TIDES). Between 2010 and 2012, the women gave blood and urine samples
in their first trimester of pregnancy and allowed researchers to take
measurements of the babies at birth.
Higher levels of two molecules that are produced when phthalates
are digested – mono-n-butyl and monobenzyl phthalate – in the mothers’
urine early in pregnancy were significantly associated with lower levels
of hCG in women carrying male babies and with higher hCG in those
carrying female babies.
The new research also looked at hCG in relation to a biological
marker called anogenital distance, which is the distance between the
anus and genitals. In men, a short anogenital distance is associated
with decreased sperm count and infertility.
Higher levels of hCG in the mother’s blood were associated with a
shorter anogenital distance in male babies. The researchers estimate
that about 20 to 30 percent of the phthalate effect on the babies’
genitals could be attributed to the influence of phthalates on hCG,
specifically mono-n-butyl and mono-ethylhexyl phthalate.
“Our study is the first to look at hCG as a target of phthalate
exposure in pregnancy,” said Dr. Adibi. “There is growing societal
concern over pediatric disorders that have a basis in the fetal period
and which may be more common in one sex or another, such as autism,
attention deficit disorder, obesity, asthma and infertility. It is
important to find out if chemicals in our food or environment might
influence these conditions.”
The participants in this study were enrolled at prenatal clinics in
California, Washington, Minnesota and New York. Dr. Adibi is looking
ahead to future studies where she will enroll women in the earliest
stages of pregnancy at clinics in Pittsburgh to assess exposures to
endocrine disruptors and measure effects on the placenta and the baby.
Additional researchers on this study are Myoung Keun Lee, M.S., of Pitt; Ashley I. Naimi, Ph.D., of McGill University; Emily Barrett, Ph.D., of the University of Rochester; Ruby Nguyen, Ph.D., and Bruce Redmon, M.D., both of the University of Minnesota; Sheela Sathyanarayana, M.D., M.P.H., of the University of Washington; and Kara Saperston, M.D., Mari-Paule Thiet, M.D., Sarah Janssen, M.D., Ph.D., M.P.H., and Lawrence Baskin, M.D., all of the University of California.