After she joined the NIEHS Epidemiology Branch this spring, tenure-track scientist Kelly Ferguson, Ph.D., focused on her research and embraced opportunities outside of the institute to talk about her work. Her most recent seminar occurred Oct. 7 at Duke University’s Integrated Toxicology and Environmental Health Program (ITEHP), part of the Nicholas School of the Environment (see text box).
Ferguson, head of the NIEHS Perinatal and Early Life Epidemiology Group, discussed how environmental exposure to phthalates, man-made compounds mostly used as plasticizers, is associated with pregnancy outcomes in U.S. women.
Phthalate exposure common
Ferguson said environmental phthalate exposure is common in the U.S. and other countries. Phthalates are included in personal care products, such as perfumes, lotions, and deodorants, as well as in soft plastics, such as vinyl flooring, shower curtains, and rain gear. Additionally, food and beverages can be a source of phthalates, from contact with plastic packaging materials.
She explained that the body metabolizes phthalates rapidly and excretes them in the urine, so scientists can measure phthalate breakdown products in urine. Research by other groups suggests these metabolite levels may be linked to adverse pregnancy outcomes and poor development of the fetus.
Crossing the placental barrier
According to Ferguson, phthalates can cross the placental barrier, and they have been detected in the placenta, umbilical cord blood, and amniotic fluid. To understand the effect phthalates have on pregnant women and their babies, she examined pregnancy outcomes in a study of preterm birth at Brigham and Women’s Hospital in Boston. The study was designed by collaborators John Meeker, Sc.D., from the University of Michigan, and Thomas McElrath, M.D., Ph.D., from Brigham and Women’s Hospital, Harvard Medical School.
Women less than 15 weeks pregnant were recruited and followed until delivery, providing urine and blood samples at four time points — 10, 18, 26, and 35 weeks of pregnancy. The researchers measured nine phthalate metabolites at each time point and found links between levels of phthalate metabolites measured early in pregnancy and with preeclampsia, a condition characterized by high blood pressure and large amounts of protein in the mother’s urine. From measurements taken later in pregnancy, they saw associations with an increase in preterm birth.
"Phthalate metabolite levels were linked to poorer fetal growth as well, although the important window of exposure was less clear," Ferguson added.
Although the study did not discover how phthalates specifically led to abnormal fetal growth, Ferguson speculated that the development of the placenta may be involved. She said that early in pregnancy, placental development could be influenced by various toxicants, causing problems with the implantation process. Later in pregnancy, other factors may affect transfer of nutrients through the placenta to the fetus.
For future work, Ferguson wants to more closely examine how chemical exposures relate to development of the placenta, growth of the fetus, and eventually lead to early life development of the child. She also plans to investigate how other environmental chemicals, as well as psychological stressors in pregnant mothers, interact to cause pregnancy complications.
Citation: Ferguson KK, McElrath TF, Meeker JD. 2013. Environmental phthalate exposure and preterm birth. JAMA Pediatr 168(1):61-67. (Story(https://factor.niehs.nih.gov/2014/1/science-preterm/index.htm))