Phthalate exposure linked to pregnancy complications
Exposure to phthalates — chemicals found in many common consumer products — may disrupt placental corticotropin-releasing hormone, causing negative pregnancy outcomes, according to a study published in Environment International.
“There is lots of evidence that placental corticotropin-releasing hormone (pCRH) is incredibly important in pregnancy, including playing a key role in the timing of birth,” Emily S. Barrett, PhD, associate professor at the Rutgers University School of Public Health, told Healio.
Phthalates, which are found in food, drinking water, cookware and clothing, can disrupt hormone activity, according to Barrett, who also is a resident faculty member of the Environmental and Occupational Health Sciences Institute at Rutgers.
“In this study, we wanted to know whether these widespread chemicals, present in 100% of Americans, could interfere with pCRH during pregnancy, potentially impacting the health of the mother and child,” she said.
The placenta produces pCRH, with levels increasing throughout pregnancy. But high levels or earlier rapid increases may contribute to preterm birth, fetal growth issues, maternal high blood pressure, maternal diabetes and even postpartum depression, the researchers said.
The study involved 1,018 women with singleton pregnancies with low medical risk between 16 and 29 weeks of gestation who received care at selected prenatal clinics in Shelby County, Tennessee, between 2006 and 2011.
With an average age of 26.4 ± 5.5 years (age range, 16 to 40 years) and a prepregnancy BMI of 27.9 ± 7.7 kg/m2, 61.4% of the participants identified as non-Hispanic Black, 32% identified as non-Hispanic white and 6.6% identified as other.
Also, 56.2% had a high school, GED or technical school education, less than 10% were smokers and 39.9% were nulliparous. While participating in the study, 59 (5.8%) and 102 (10%) of the women developed gestational diabetes and gestational hypertension, respectively.
The researchers collected spot urine samples during two visits to the clinic, the first between 16 and 29 weeks of gestation and the second between 22 and 39 weeks of gestation.
Next, the researchers used enzymatic deconjugation, solid phase extraction and high-performance liquid chromatography tandem mass spectrometry to assay a panel of 21 phthalate metabolites.
There was a positive association between the phthalate mixture and pCRH at the first visit (B = 0.07; 95% CI, 0.02-0.11), but at the second visit, there was an inverse relationship (B = –0.08; 96% CI, –0.14 to –0.02). In other words, the presence of various phthalates was associated with higher levels of pCRH in mid-pregnancy but lower pCRH later in pregnancy, the researchers said.
“What came as a surprise, however, is that the associations were much stronger in women who developed pregnancy complications such as preeclampsia and gestational diabetes,” Barrett said.
Among the participants who developed gestational diabetes, there was a significant inverse association between a mixture of phthalates and pCRH during the second visit (B = –0.35; 95% CI, –0.5 to –0.19; permutation test, P < .005).
The participants who developed gestational hypertension saw a positive association between phthalates and pCRH at the first visit (B = 0.2; 95% CI, 0.03-0.36) and the second visit (B = 0.42; 95% CI, 0.19-0.64; permutation test, P = .005).
“This tells us that medically high-risk women may be particularly vulnerable to the impacts of chemicals in our environment, which is something that has not been studied previously,” Barrett said.
“This is yet another reason why women who are pregnant or planning a pregnancy should be careful about the products they use and foods they eat, choosing items that are phthalate-free whenever possible,” she continued.
However, the data do not clearly support the hypothesis that phthalates contribute to preterm birth through the pCRH pathway, according to the researchers, who plan to continue their investigations.
“As one of the first studies on this topic, it is important to first replicate this work,” Barrett said. “In light of the fact that we are all exposed to dozens if not hundreds of environmental chemicals daily, we are now studying other chemicals that interfere with hormone levels to see how they impact pCRH and the course of pregnancy as well.”