Phthalate levels in urine of pregnant women and their associated missed abortion risk

Individual and joint effects of phthalates exposure on the risk of early miscarriage

BACKGROUND

The exposure levels of phthalates in humans have dropped dramatically. Little is known about the individual and joint effects of phthalates exposure at low levels on the risk of early miscarriage.

OBJECTIVE

To examine the association between exposure to phthalates individually or as a mixture and early miscarriage.

METHODS

A case-control study was conducted in Shanghai, China during 2019-2020. A total of 291 women seeking medical services due to miscarriage (cases) and 308 women planning to terminate an unintended pregnancy (controls) within 12 gestational weeks were recruited. Urinary concentrations of eight phthalate metabolites were determined by ultra-performance liquid chromatography. We included 534 women in the main analysis who had available data on both phthalates exposure and complete information on potential confounders. We used logistic regression and Bayesian kernel machine regression (BKMR) to examine the associations of concentrations of phthalates with miscarriage.

RESULTS

Among the phthalate metabolites, mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) had the highest concentration (8.10 ng/mL), followed by mono(2-ethyl-5-oxohexyl) phthalate (MEOHP, 2.68 ng/mL) and monobutyl phthalate (MBP, 2.24 ng/mL). Higher concentrations of MBP, mono(2-ethylhexyl) phthalate (MEHP), MEHHP, MEOHP and the molar sum of di(2-ethylhexyl) phthalate (DEHP) metabolites (∑DEHPm) were associated with an increased risk of miscarriage exhibiting a dose-response relationship. The most evident association of miscarriage was found with ∑DEHPm, with adjusted odds ratio (95% confidence interval) of 1.94 (1.14, 3.31) for the second quartile, 2.83 (1.67, 4.79) for the third quartile and 4.28 (2.49, 7.37) for the fourth quartile compared to the first quartile. Consistently, the phthalate mixture was positively associated with the risk of miscarriage and DEHP was the predominant contributor to the joint effect in BKMR model.

IMPACT

Phthalates are a family of synthetic chemicals mainly used as plasticizers, solvents and additives in a large variety of industrial and consumer products, including food packing materials, toys, gloves, medical devices and personal care products. Although exposure levels of phthalates of pregnant women have declined sharply over the past few decades, phthalates exposure was still associated with an increased risk of early miscarriage. Our findings suggest that future researchers and policy makers might need to take low-dose effects of phthalates into account regarding the reproductive toxicity of phthalates exposure in humans.

SIGNIFICANCE

Our findings contribute to the awareness of the reproductive toxic potential of phthalates at low levels in humans and support the ongoing efforts to further reduce exposure to phthalates.

Influence of maternal endocrine disrupting chemicals exposure on adverse pregnancy outcomes: A systematic review and meta-analysis

Maternal endocrine disrupting chemicals (EDCs) exposure, the common environmental pollutants, was capable of involving in adverse pregnancy outcomes. However, the evidence of their connection is not consistent. Our goal was to comprehensively explore the risk of EDCs related to adverse pregnancy outcomes. One hundred and one studies were included from two databases before 2023 to explore the association between EDCs and adverse pregnancy outcomes including miscarriage, small for gestational age (SGA), low birth weight (LBW) and preterm birth (PTB). We found that maternal PFASs exposure was positively correlated with PTB (OR:1.13, 95% CI:1.04-1.23), SGA (OR:1.10, 95% CI:1.04-1.16) and miscarriage (OR:1.09, 95% CI:1.00-1.19). The pooled estimates also showed maternal PAEs exposure was linked with PTB (OR:1.16, 95% CI:1.11-1.21), SGA (OR:1.20, 95% CI:1.07-1.35) and miscarriage (OR:1.55, 95% CI:1.33-1.81). In addition, maternal exposure to some specific class of EDCs including PFOS, MBP, MEHP, DEHP, and BPA was associated with PTB. Maternal exposure to PFOS, PFOA, PFHpA was associated with SGA. Maternal exposure to BPA was associated with LBW. Maternal exposure to MMP, MEHP, MEHHP, MEOHP, BPA was associated with miscarriage. Maternal PFASs, PAEs and BPA exposure may increase adverse pregnancy outcomes risk according to our study. However, the limited number of studies on dose-response hampered further explanation for causal association.

Phthalates (PAEs) and reproductive toxicity: Hypothalamic-pituitary-gonadal (HPG) axis aspects

Phthalates (PAEs) are widely used for their excellent ability to improve plastic products. As an essential endocrine axis that regulates the reproductive system, whether dysfunction of the hypothalamic-pituitary-gonadal (HPG) axis is involved in reproductive toxicity mediated by environmental endocrine disruptors PAEs has become a hot topic of widespread concern. This study systematically reviewed the adverse effects of multiple PAEs on the HPG axis in different models and objectively discussed the possible underlying mechanisms. The abnormal release of gonadotropin-releasing hormone and gonadotropin, dysfunction of sex hormone receptors and steroid hormone synthesis, and general damage, including cell proliferation, oxidative stress, apoptosis, and autophagy have been confirmed to be involved in this process. Although it is widely established that PAEs induce HPG axis dysfunction, the specific mechanisms involved remain unclear. From a systematic review of relevant publications, it appears that the abnormal expression of peroxisome proliferator-activated, aryl hydrocarbon, and insulin receptors mediated by PAEs is key upstream event that induces these adverse outcomes; however, this inference needs to be further verified. Overall, this study aimed to provide reliable potential biomarkers for future environmental risk assessment and epidemiological investigation of PAEs.

Maternal urine phthalate metabolite exposure and miscarriage risk: a nested case-control study of the Zunyi Birth Cohort

Phthalates (PAEs) are widespread persistent organic pollutants and endocrine disruptors. However, the associations between PAE exposure and the risk of miscarriage in humans are unclear, and an insufficient number of studies have evaluated the possible threshold or dose-dependent effects of first trimester PAE exposure on miscarriage risk. Our research measured the levels of mono-methyl phthalate (MMP), mono-ethyl phthalate, mono-isobutyl phthalate, MiBP mono-butyl phthalate (MBP), mono-octyl phthalate, mono-benzyl phthalate, mono(2-ethylhexyl) phthalate, mono(2-ethyl-5-oxohexyl) phthalate, and mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) in maternal urine collected in early gestation between 150 pregnancies ending in miscarriage and 150 pregnancies with live birth. We also estimated the odds ratios (ORs) and 95% confidence intervals (CIs) for miscarriage and each PAE as a continuous variable or quartile. A restrictive cubic splines was used to assess dose-dependent effects after controlling for maternal characteristics (e.g., age, educational level). we identified monotonically increasing dose-dependent effects of MEHHP and MMP on the risk of miscarriage. The largest effect estimates were approximately threefold higher for the highest MBP (OR = 2.57; 95% CI = 1.32-5.01) or MMP quartile (OR = 3.57; 95% CI = 1.82-7.00) and two-fold higher for the highest MEHHP quartile (OR = 2.12; 95% CI = 1.10-4.11). Our research preliminarily obtained possible thresholds of MBP, MEHHP, and MMP which were 18.07, 2.38, and 0.80 µg/g Cr for the risk of miscarriage, respectively. First-trimester exposure to MBP, MEHHP, and MMP exceeding certain thresholds increases the risk of miscarriage.

How many missed abortions are caused by embryonic chromosomal abnormalities and what are their risk factors?

Introduction: Though embryonic chromosome abnormalities have been reported to be the most common cause of missed abortions, previous studies have mainly focused on embryonic chromosome abnormalities of missed abortions, with very few studies reporting that of non-missed abortion. Without chromosome studies of normal abortion samples, it is impossible to determine the risk factors of embryo chromosome abnormalities and missed abortion. This study aimed to investigate the maternal and embryonic chromosome characteristics of missed and non-missed abortion, to clarify the questions that how many missed abortions are caused by embryonic chromosomal abnormalities and what are their risk factors. Material and methods: This study was conducted on 131 women with missed or non-missed abortion from the Longitudinal Missed Abortion Study (LoMAS). Logistic regression analysis was used to identify the association between maternal covariates and embryonic chromosomal abnormalities and missed abortions. Data on the characteristics of women with abortions were collected. Results: The embryonic chromosome abnormality rate was only 3.9% in non-missed abortion embryos, while it was 64.8% in missed-abortion embryos. Assisted reproductive technology and prior missed abortions increased the risk of embryonic chromosome abnormalities by 1.637 (95% CI: 1.573, 4.346. p = 0.010) and 3.111 (95% CI: 1.809, 7.439. (p < 0.001) times, respectively. In addition, as the age increased by 1 year, the risk of embryonic chromosome abnormality increased by 14.4% (OR: 1.144, 95% CI: 1.030, 1.272. p = 0.012). Moreover, advanced age may lead to different distributions of chromosomal abnormality types. Conclusion: Nearly two-thirds of missed abortions are caused by embryonic chromosomal abnormalities. Moreover, advanced age, assisted reproductive technology, and prior missed abortions increase the risk of embryonic chromosomal abnormalities.

Female Reproductive Health and Exposure to Phthalates and Bisphenol A: A Cross Sectional Study

The xenoestrogenicity of some plasticisers (phthalates and bisphenol A) is documented in the literature and may pose a risk to female reproductive health. The aim of this study was to assess exposure to six phthalates. This was achieved by measuring their respective metabolites (mono-ethylphthalate (MEP); mono-n-butylphthalate (MnBP); mono-n-ottylphthalate (MnOP); and monobenzylphthalate (MBzP)), as well as the sum of two of the diethyl-hexyl phthalate metabolites-(∑DEHP) and bisphenol A (BPA) in a female population with infertility problems, and by conducting a correlation analysis between infertility factors, work activities, and lifestyle habits, in order to formulate a causal hypothesis. A cross-sectional epidemiological study was carried out and women under 43 years of age were recruited from an assisted reproduction technology (ART) center; the sample of 186 women was given a specific questionnaire and a spot urine sample was collected. Phthalate metabolites and urinary BPA were analyzed by HPLC/MS/MS. The results showed significantly higher mean values for MEP in women with recurrent pregnancy loss (RPL) (820.5 ± 1929.5 µg/g of creatinine) and idiopathic infertility (230.0 ± 794.2 µg/g of creatinine) than in women with other infertility factors (76.9 ± 171.8 µg/g of creatinine). Similarly, for MnOP levels, women with idiopathic infertility (2.95 ± 3.44 µg/g of creatinine) showed significantly higher values than women with the other infertility factors taken together (1.35 ± 2.05 µg/g of creatinine). Women with tubal factors of infertility, RPL, and endocrine dysfunctions show higher values of DEHP (p = 0.032). Considering occupations, women working in commerce showed more than twice as much urinary BPA levels (1.10 ± 0.48 µg/g of creatinine) compared to women working in other industries (0.45 ± 0.35 µg/g of creatinine). The presence of significantly higher values of certain phthalates, DEHP in particular, especially in women with RPL and idiopathic infertility, suggests a possible involvement of these compounds as competing factors in reproductive issues. The study of sources of exposure suggested that the working activity in trade, as a casher in particular, represents a major one for BPA (p = 0.015).