Exposure to phthalates through maternal blood and cord blood affected outcomes including head circumference and anogenital index for male and female infants, according to data from 65 mother-infant pairs.
Phthalates are recognized endocrine disruptors that have been associated with adverse birth outcomes, but the specific relationship between maternal phthalate exposure and birth outcomes has not been well studied, wrote Hsiao-Lin Hwa, MD, of National Taiwan University, Taipei, and colleagues.
Previous research suggests that trace exposure to hazardous chemicals during the fetal period “may cause fetal metabolic dysfunction and adversely change the morphology of body systems,” they said. In 2011, “the Taiwan Food and Drug Administration found that di‐2‐ethylhexyl phthalate (DEHP) and DiNP [di‐isononyl phthalate] had been illegally added as emulsifiers to replace palm oil in beverages and food,” they added. The researchers sought to examine the association between infant birth outcomes and phthalate exposure levels in the Taiwanese population after 2011. In a study published in Environmental Toxicology and Chemistry, the researchers recruited 65 pregnant women in Taiwan between 2016 and 2017. Birth length, birth weight, head circumference, anogenital distance (AGD), anoscrotal distance (ASD), and anofourchette distance (AFD) were measured for each newborn at the time of delivery. The average age of the women was 33.6 years, and the rate of low birth weight was 13.7%. The mean measures of birth length, birth weight, head circumference, and chest circumference were 47.6 cm, 3022 g, 32.9 cm, and 30.8 mm, respectively. The mean AFD and ASD were 14.2 mm and 22.3 mm, respectively.
The researchers tested for 12 phthalates in maternal blood and cord blood samples. Of these, the six most frequently detected phthalate metabolites were mono‐ethyl phthalate (MEP), mono‐isobutyl phthalate (MiBP), mono‐n‐butyl phthalate (MnBP), mono‐(2‐ethyl‐5‐oxohexyl)‐phthalate (MEOHP), mono‐(2‐ethyl‐5‐hydroxyhexyl) phthalate (MEHHP), and mono‐n‐octyl phthalate (MOP); these six were present in 80%–100% of the maternal blood samples.
Overall, the mean levels of MEP, MiBP, MnBP, and MEHP were relatively higher in both maternal and infant blood than other phthalates, the researchers noted. The mean concentrations of metabolites in maternal blood and infant cord blood were 0.03-2.27 ng/mL and 0.01-3.74 ng/mL, respectively.
Among male infants, levels of MMP, MiBP, and MEHP in maternal blood were inversely related to anogenital index (AGI), with P values for regression coefficients ranging from .011 to .033. In addition, the total concentration of MEHP, MEOHP, and MEHHP (designated as Σdi‐2‐ethylhexyl phthalate, ΣDEHP) was inversely related to AGI in males.
Among female infants, however, phthalates in cord blood, rather than maternal blood, were positively related to AGI, including MMP, MibP, MnBP, and MOP, with P values for regression coefficients ranging from .001 to .034.
Cord blood levels of MnBP, MEOHP, MEHP, and ΣDEHP were inversely associated with gestational age-adjusted head circumference in all infants, with beta coefficients of –0.15, –0.12, –0.01, and –0.01, respectively (P < .05 for all).
“The detection rates of MEHHP, MEOHP, and MEHP in the cord blood were lower than those in the maternal blood, particularly those of MEHHP and MEOHP, which were approximately 25% lower,” which may be caused by slow placental transfer, the researchers wrote in their discussion section. “The high detection rate of phthalate metabolites indicated that our subjects may continue to be exposed to these phthalates even after the 2011 Taiwan DEHP incident,” they noted.
The study findings were limited by several factors including the possibility for contamination of samples and other environmental confounders, the researchers noted. However, the results support the role of phthalates as endocrine disruptors, and the distinction in effects between males and females “may suggest that phthalate monoesters are potentially estrogenic and antiandrogenic chemicals,” they added.
“Further investigations involving multiple phthalate analyses during pregnancy and measurements throughout childhood are necessary to confirm our findings,” they concluded.