Phthalate exposure during pregnancy and its relationship with birth outcomes in Guangzhou

Background Phthalates (PAEs) are ubiquitous chemical plasticizers and are known endocrine disruptors that are toxic to reproduction.

Objective This study aims to investigate the effect of exposure to PAEs on birth outcomes among pregnant women in Guangzhou.

Methods The participants were 848 pregnant women from a premature birth cohort in Huadu District, Guangzhou City from October 2017 to June 2019. Questionnaires were distributed to collect the demographic information, lifestyle, and birth outcomes of pregnant women, and maternal blood and cord blood samples were also collected after delivery. The concentrations of five PAEs metabolites in maternal blood and cord blood were determined by high-performance liquid chromatography-tandem mass spectrometry, including mono(2-ethylhexyl) phthalate (MEHP), monobenzyl phthalate (MBzP), monobutyl phthalate (MnBP), monomethyl phthalate (MMP), and monoethyl phthalate (MEP). The correlations of PAEs metabolites with the birth weight Z-score of term infants, spontaneous premature, and small for gestational age (SGA) were evaluated.

Results The selected five PAEs were all positive in maternal blood and cord blood samples.The positive rates were all above 98.94% except for MBzP. The concentrations (geometric mean and 95% CI) of MEHP, MnBP, MMP, and MEP in maternal blood were 11.48 (11.04-11.95), 27.50 (26.07-29.01), 1.98 (1.89-2.07), and 0.30 (0.29-0.32) μg·L^-1, respectively; while the concentrations in cord blood were 6.78 (6.45-7.12), 36.22 (34.61-37.91), 2.54 (2.41-2.67), and 0.34 (0.33-0.36) μg·L^-1, respectively. The concentrations of the four PAEs metabolites in cord blood were all correlated to the concentrations in maternal blood (P < 0.001): The largest correlation coefficient was for MMP (r=0.585), and the smallest was for MEHP (r=0.286). After controlling for pregnant age, passive smoking time during pregnancy, pregnancy complications, and other related factors, the birth weight Z-score of the 747 term infants was negatively associated with MEHP concentration in maternal blood (b=-0.129, 95% CI: -0.219--0.038). In cord blood, a greater MEP concentration was associated with a lower risk for spontaneous preterm (OR=0.655, 95% CI: 0.436-0.985), but with a higher risk for SGA (OR=1.574, 95%CI: 1.063-2.331).

Conclusion The pregnant women in Guangzhou are widely exposed to PAEs and intrauterine exposure level is high. Intrauterine exposure to PAEs affect pregnancy outcomes by increasing gestational age while reducing birth weight.