Urinary phthalate metabolite concentrations in relation to history of infertility and use of assisted reproductive technology

Use of Chemical Hair Straighteners and Fecundability in a North American Preconception Cohort

Chemical hair straighteners ("relaxers") are used by millions of North Americans, particularly women of color. Hair relaxers may contain endocrine-disrupting compounds, which can harm fertility. We evaluated the association between hair relaxer use and fecundability among 11,274 participants from Pregnancy Study Online (PRESTO), a North American preconception cohort study. During 2014-2022, participants completed a baseline questionnaire in which they reported their history of relaxer use and completed follow-up questionnaires every 8 weeks for 12 months or until pregnancy, whichever came first. We used multivariable-adjusted proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs). Relative to never use, fecundability was lower among current (FR = 0.81, 95% CI: 0.64, 1.03) and former (FR = 0.89, 95% CI: 0.81, 0.98) users of hair relaxers. FRs for first use of hair relaxers at ages <10, 10-19, and ≥20 years were 0.73 (95% CI: 0.55, 0.96), 0.93 (95% CI: 0.83, 1.04), and 0.85 (95% CI: 0.74, 0.98), respectively. Fecundability was lowest among those with longer durations of use (≥10 years vs. never: FR = 0.71, 95% CI: 0.54, 0.91) and more frequent use (≥5 times/year vs. never: FR = 0.82, 95% CI: 0.60, 1.11), but associations were nonmonotonic. In this preconception cohort study, use of chemical hair straighteners was associated with slightly reduced fecundability.

Subfertile patients underestimate their risk factors of reprotoxic exposure

Background

Exposure of men and women to environmental reprotoxic agents is associated with impaired fertility and pregnancy rates after assisted reproductive treatment (ART). Nevertheless, such exposures are generally not systematically assessed in current practice before ART and subfertile men are generally less explored than women. Our objective was to study subfertile men and women’s level of knowledge about reprotoxic agents, their perception of their own risk factors and the correlation between perceived and identified circumstances of exposure.

Results

In our public university hospital, 390 subfertile patients (185 men and 185 women) requiring assisted reproduction technique (ART) treatment, completed a self-report questionnaire before consultation, in order to assess patients’ knowledge of reprotoxic exposures, sources of information about them and perception of their own circumstances of exposure. Then a standardized questionnaire was used by the physician during the consultation to estimate domestic, environmental and occupational risk factors of reprotoxic exposures (RFRE). We compared the patients’ perception of exposure with the estimated RFRE.

The reprotoxic agents knowledge score of patients was 61%. Their main sources of information were the media (40%), the internet (22%) and gynecologists (15%). The standardized questionnaire identified RFRE in 265/390 patients (68%); risk factor was statistically more frequent in men (77%) than in women (59%) (p < 0.05). In total, 141 of the 265 patients with identified RFRE (53%) were aware of their risk factor of reprotoxic exposure.

Conclusion

We identified risk factors of reprotoxic exposures in the majority of subfertile patients, more frequently in men than in women, and half of patients were not aware of their exposures. Patients’ main sources of information were extra medical. Efforts should be made to inform patients, especially men, about potential reprotoxic exposure and to enhance medical training about reprotoxic agents, as recommended by international guidelines. The detection and correction of environmental exposures in subfertile men could improve their fecundity, but also their general health, which has been shown to be poorer than health of fertile men.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12610-022-00161-z.

Knowledge, Attitudes, and Behaviors Regarding Chemical Exposure among a Population Sample of Reproductive-Aged Women

We examined the knowledge and attitudes of reproductive-age women toward environmental chemicals and determined how these affect consumer behaviors. At the 2018 Minnesota State Fair, a large community sample of reproductive-age women was recruited to complete a survey on environmental health attitudes and behaviors. Descriptive statistics, chi-square tests, and logistic regression models were used to characterize current attitudes about chemicals. Multivariable logistic regression models examined how sociodemographic characteristics predict knowledge, attitudes, and consumer behaviors. A total of 871 women completed the survey; 74% strongly agreed that chemicals in the environment are dangerous, and 44% of women reported having heard of phthalates, while only 29% reported always practicing at least one environmentally healthy behavior (such as consuming food and beverages from safe plastics). Older age (35-39 versus 18-24: aOR 2.3, 95% CI 1.3, 4.3; 40-44 versus 18-24; aOR 2.0, 95% CI 1.2, 3.2) and working in a healthcare profession (aOR: 1.7, 95% CI: 1.2, 2.5) were associated with strong agreement that chemicals in the environmental are dangerous. Women who strongly agreed chemicals are dangerous were more likely to practice consumer behaviors to reduce their exposure. Interventions targeting knowledge and attitudes towards environmental chemicals could be an effective strategy for reducing harmful exposures.

Association between phthalate exposure and risk of spontaneous pregnancy loss: A systematic review and meta-analysis

Numerous studies suggested that phthalates might be associated with increased risk of spontaneous pregnancy loss. However, these results were conflicting and inconclusive. Thus we performed this systematic review and meta-analysis to assess the relationship between phthalate exposure and risk of pregnancy loss. We searched PubMed, EMBASE, Web of Science and major Chinese literature databases for studies investigating phthalates and spontaneous pregnancy loss. Pooled odds ratio (OR) with 95% confident interval (CI) were calculated for risk estimate. A total of 8 studies involving 4713 participants (including 651 cases and 4062 controls) were enrolled in the present meta-analysis. Our pooled results showed that spontaneous pregnancy loss was associated with higher urinary levels of monobutyl phthalate (MBP) (OR: 1.34, 95% CI: 1.04-1.72), mono(2-ethylhexyl) phthalate (MEHP) (OR: 1.57, 95% CI: 1.29-1.90), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) (OR: 1.59, 95% CI: 1.23-2.07) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) (OR: 1.47, 95% CI: 1.15-1.89). Indirect estimate of di-2-ethylhexyl phthalate (DEHP) levels, which were pooled from molar sum of urinary DEHP metabolites and hair DEHP, were also correlated with elevated risk of spontaneous pregnancy loss (OR: 1.79, 95% CI: 1.27-2.53). No significant association was found regarding urinary concentrations of monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-isobutyl phthalate (MiBP), monobenzyl phthalate (MBzP) or mono(2-ethyl-5-carboxypentyl) phthalate (MECPP). Our findings indicate that phthalate exposure might be a risk factor for spontaneous pregnancy loss. Given indirect estimate of phthalate exposure by evaluating its metabolite levels, our results should be interpreted with caution.

Pregnancy intention and phthalate metabolites among pregnant women in The Infant Development and Environment Study cohort

BACKGROUND

Preconception life style and health play a pivotal role in positively impacting the health of a pregnancy, and this includes the reduction of exposure to endocrine-disrupting chemicals such as phthalates. We have previously demonstrated that women planning a pregnancy with assisted reproductive technology (ART) have lower phthalate metabolite concentrations than their non-ART-using counterparts.

OBJECTIVE

To determine whether women who intended to become pregnant had lower phthalate metabolite concentrations than those who had an unintended pregnancy, or whether change in phthalate exposure across pregnancy differed between these two groups.

METHODS

A total of 721 women enrolled in The Infant Development and Environment Study (TIDES), a multicentre US prospective pregnancy cohort; 513 (71%) indicated their pregnancy was planned. Urine samples from first- and third-trimester visits were analysed for 10 specific-gravity-adjusted, natural-log-transformed phthalate metabolites. Simple and multivariable linear regression, adjusting for centre, race, age, income, marital status, and parity, were employed to determine whether phthalate metabolite concentrations differed by pregnancy intention.

RESULTS

In bivariate analyses, the geometric mean concentrations of all first-trimester and most third-trimester phthalates were higher in women with unplanned pregnancies. However, after covariate adjustment, only first-trimester monoisobutyl phthalate (MiBP) remained associated with pregnancy intention, and the association changed direction such that unplanned pregnancies had lower MiBP concentrations (ß -0.18, 95% CI -0.35, -0.02).

CONCLUSIONS

We did not find evidence of a difference in phthalate exposure between pregnancy planners and non-planners.

Nonpersistent endocrine disrupting chemicals and reproductive health of women

Nonpersistent endocrine disrupting chemicals (npEDCs) are exogenous chemicals or mixtures of industrial agents that can interfere with the normal action of hormone with a shorter half-life and lower liposolubility. These are commonly found in plastics, medical equipment, detergents, and cosmetics. Recently, role of npEDCs on the changes of ovary and/or uterus development and alterations in hormonal signaling has been emphasized. However, many controversial results exist on the effects of npEDCs and reproductive health of women. Thus, we have focused to review the scientific evidence of a causal relationship between exposure to npEDCs and representative female reproductive issues such as menstrual cycle, endometriosis, uterine fibroids, polycystic ovarian syndrome and infertility/subfertility. Though not all studies indicated a positive correlation of npEDCs with female reproductive issues, the reviewed data illustrated that the majority of the available data strengthen the evidence of reproductive health-related actions of npEDCs. In future, recommendations should be made in order to reduce human exposure to npEDCs and to protect from steadily increasing reproductive health risks.

The extent and predictors of phthalate exposure among couples undergoing in vitro fertilization treatment

Phthalates are chemicals used as plasticizers and solvents in many consumer products but are suspected of disrupting the endocrine system and are known for their reproductive/developmental health risks. This study examined the extent and predictors of phthalate exposure among 599 couples undergoing in vitro fertilization. A questionnaire was administered to obtain sociodemographic, health, and lifestyle data, and two spot urine samples were collected from the couples to analyze eight phthalate metabolites, cotinine (COT) as a smoking index, and creatinine to adjust for urine dilution. Seven phthalate metabolites were detected in > 94% of the urine samples, and monobenzyl phthalate (MBzP) was found in 24% of the women and 26% of their male partners. Median phthalate levels were highest for monoethyl phthalate (MEP), at 333.26 μg/l in women and 290 μg/l in male partners, and lowest for MBzP, at 1.17 μg/l in women and 1.14 μg/l in male partners. Correlation coefficients of ≥ 0.4 between the women and their male partners for the eight urinary phthalate metabolites may indicate a shared source of exposure. A multivariate regression model was used to assess the association between predictors and each urinary phthalate metabolite. Several potential predictors for the variations in specific urinary phthalate metabolites were identified, including the body mass index, age, socioeconomic status, and regional distribution for both women and their male partners but with slightly different patterns. Women with a history of breastfeeding, using bottled water for cooking and storing food in plastic bags had lower MEP (8.7%), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP) (9.2%), and both mono-iso-butyl phthalate and MECPP (8.2 and 8.1%). A history of contraceptive use was associated with an increase in MECPP (8.7%), mono-(2-ethyl-5-hydroxyhexyl) phthalate (11.4%), mono-(2-ethyl-5-oxohexyl) phthalate (7.6%), and the molar sum of bis (2-ethylhexyl) phthalate metabolites (8.9%). Urinary COT levels were associated with an increase of 10-16% in all urinary metabolites in women but of only 10.5% in mono-(2-ethylhexyl) phthalate in male partners. More than 95% of the couples reported the use of cosmetics, perfumes, and personal-care products, but we were not able to find associations with urinary phthalate metabolites, perhaps due to their short half-lives. MEP levels associated with the use of household cleaning products were 11.2% higher in male partners. Our levels were generally higher than those reported elsewhere, perhaps due to different lifestyles, cultural practices, dietary habits, use of personal-care products, and governmental legislation.

Exposure to phthalates in couples undergoing in vitro fertilization treatment and its association with oxidative stress and DNA damage

This prospective study of 599 couples seeking fertility treatment and who were recruited between 2015 and 2017 was conducted to (a) explore the associations between phthalate exposure and in vitro fertilization (IVF) outcomes; and (b) examine the implication of oxidative stress as a mediator of these. We measured eight phthalate metabolites in two spot urine samples; oxidative stress biomarkers such as malondialdehyde, 8-hydroxy-2-deoxyguanosine, hydrogen peroxide, catalase (CAT), and total antioxidant capacity in follicular fluid and seminal plasma. We also examined DNA damage in sperm and granulosa cells. Couples were exposed to a broad range of phthalate compounds and seven metabolites were detected in over 94% of the urine samples, whereas monobenzyl phthalate was found in only 24% of women and 26% of men. Our results showed high levels of seven urinary phthalate metabolites (except monobenzyl phthalate) and a notable increase in many oxidative stress markers in both follicular fluid and seminal plasma. However, their associations with exposure were rather limited. Multivariate binomial regression modeling showed higher levels of follicular CAT levels reduced the probability of fertilization rate (≤ 50%) [Adjusted relative risk (RR_adj) = 0.52, p = 0.005] and unsuccessful live birth (RR_adj = 0.592, p = 0.023). We observed a 46% decrease in the probability of clinical pregnancy in association with an elevated percentage of DNA in the tail (RR_adj = 0.536, p = 0.04). There was a 32% and 22% increase in the probability of clinical pregnancy and unsuccessful live birth associated with higher levels of mono-(2-ethylhexyl) phthalate (RR_adj = 1.32, p = 0.049) and monoethyl phthalate (RR_adj = 1.22, p = 0.032) in women, respectively. In contrast, the probability of clinical pregnancy reduced by 20% with higher levels of mono-(2-ethyl-5-carboxypentyl) phthalate (RR_adj = 0.797, p = 0.037) and 19.6% with mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) (RR_adj = 0.804, p = 0.041) in men. Other oxidative stress biomarkers or urinary phthalate metabolites showed suggestive relationships with certain IVF outcomes. Lastly, our results demonstrated that elevated levels of CAT in follicular fluid might have a positive impact on fertilization rate ≥ 50% and successful live birth. CAT seems to play a potential role in mediating the relationship between the risk of poor fertilization rate and MEOHP and mono-isobutyl phthalate. Additional data are required to understand the clinical implications of oxidative stress and its contribution to the reproductive toxicity of phthalate exposure.

Water and soil pollution as determinant of water and food quality/contamination and its impact on female fertility

A mounting body of the literature suggests that environmental chemicals found in food and water could affect female reproduction. Many worldwide daily-used products have been shown to contain chemicals that could incur adverse reproductive outcomes in the perinatal/neonatal periods, childhood, adolescence, and even adulthood. The potential impact of Bisphenol A (BPA), Phthalates and Perfluoroalkyl substances (PFAS) on female reproduction, in particular on puberty, PCOS pathogenesis, infertility, ovarian function, endometriosis, and recurrent pregnancy loss, in both humans and animals, will be discussed in this report in order to provide greater clinician and public awareness about the potential consequences of these chemicals. The effects of these substances could interfere with hormone biosynthesis/action and could potentially be transmitted to further generations. Thus proper education about these chemicals can help individuals decide to limit exposure, ultimately alleviating the risk on future generations.

Exposure to non-persistent chemicals in consumer products and fecundability: a systematic review

BACKGROUND

Exposure to non-persistent chemicals in consumer products is ubiquitous and associated with endocrine-disrupting effects. These effects have been linked to infertility and adverse pregnancy outcomes in some studies and could affect couple fecundability, i.e. the capacity to conceive a pregnancy, quantified as time to pregnancy (TTP).

OBJECTIVE AND RATIONALE

Few epidemiologic studies have examined the impact of non-persistent chemicals specifically on TTP, and the results of these studies have not been synthesized. We undertook a systematic review to summarize the strength of evidence for associations of common non-persistent chemicals with couple fecundability and to identify gaps and limitations in the literature, with the aim of informing policy decisions and future research.

SEARCH METHODS

We performed an electronic search of English language literature published between 1 January 2007 and 25 August 2017 in MEDLINE, EMBASE.com, Global Health, DART/TOXLINE, POPLINE and DESTAF. We included human retrospective and prospective cohort, cross-sectional and case-control studies that examined phthalates, bisphenol A, triclosan, triclocarban, benzophenones, parabens and glycol ethers in consumer products, and considered TTP or fecundability as an outcome among women, men and couples conceiving without medical assistance. We excluded editorials, opinion pieces, introductions to special sections, articles that described only lifestyle (e.g. caffeine, stress) or clinical factors (e.g. semen parameters, IVF success). Standardized forms for screening, data extraction and study quality were developed using DistillerSR software and completed in duplicate. We used the Newcastle-Ottawa Scale to assess risk of bias and devised additional quality metrics based on specific methodological features of fecundability studies.

OUTCOMES

The search returned 3456 articles. There were 15 papers from 12 studies which met inclusion criteria, of which eight included biomarkers of chemical exposure. Studies varied widely in terms of exposure characterization, precluding a meta-analytic approach. Among the studies that measured exposure using biospecimens, results were equivocal for associations between either male or female phthalate exposure and TTP. There was preliminary support for associations of female exposure to some parabens and glycol ethers and of male exposure to benzophenone with longer TTP, but further research and replication of these results are needed. The results provided little to no indication that bisphenol A, triclocarban or triclosan exposure was associated with TTP.

WIDER IMPLICATIONS

Despite a growing literature on couple exposure to non-persistent endocrine-disrupting chemicals and fecundability, evidence for associations between biologically measured exposures and TTP is limited. Equivocal results with different non-persistent chemical compounds and metabolites complicate the interpretation of our findings with respect to TTP, but do not preclude action, given the documented endocrine disrupting effects on other reproductive outcomes as well as fetal development. We therefore advocate for common-sense lifestyle changes in which both females and males seeking to conceive minimize their exposure to non-persistent chemicals.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42018084304.

Increased Urinary Phthalate Levels in Women with Uterine Leiomyoma: A Case-Control Study

We assessed the urinary concentration of 16 phthalate metabolites in 57 women with and without uterine leiomyoma (n = 30 and 27; respectively) to determine the association between phthalate exposure and uterine leiomyoma. To evaluate exposure to di-(2-ethylhexyl) phthalate (DEHP); we calculated the molar sum of DEHP metabolites; ∑3-DEHP (combining mono-(2-ethylhexyl) phthalate (MEHP); mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP); and mono-(2-ethyl-5-oxohexyl) phthalate); ∑4-DEHP (∑3-DEHP plus mono-(2-ethyl-5-carboxypentyl) phthalate); and ∑5-DEHP (∑4-DEHP plus mono (2-(carboxylmethyl)hexyl) phthalate (2cx-MMHP)). The log transformed urinary levels of MEHP; MEHHP; 2cx-MMHP; ∑3-DEHP; ∑4-DEHP; and ∑5-DEHP in the leiomyoma group were significantly higher than those of controls. When we adjusted for age; waist circumference; and parity using multiple logistic regression analyses; we found log ∑3-DEHP (OR = 10.82; 95% CI = 1.25; 93.46) and ∑4-DEHP (OR = 8.78; 95% CI = 1.03; 75.29) were significantly associated with uterine leiomyoma. Our findings suggest an association between phthalate exposure and uterine leiomyoma. However; larger studies are needed to investigate potential interactions between phthalate exposure and uterine leiomyoma.

Racial/ethnic disparities in environmental endocrine disrupting chemicals and women's reproductive health outcomes: epidemiological examples across the life course

Disparities in women's reproductive health outcomes across the life course have been well-documented. Endocrine disrupting chemicals may be one factor driving disparities, as studies suggest exposure to certain environmental endocrine disrupting chemicals, such as certain phthalates, bisphenol A, parabens and polybrominated diphenyl ethers are higher in non-whites. Yet, a limited amount of research has focused on these chemical exposures as a potential mediator of racial/ethnic differences in women's reproductive health outcomes, such as pubertal development, fibroids, infertility, and pregnancy complications. Given that race/ethnicity is a social construct, the purpose of this review was to present the current state of the literature on racial/ethnic disparities in both environmental endocrine disrupting chemicals, as well as associations between these chemicals and selected women's reproductive health outcomes. Our goal was to evaluate literature from populations based in the United States to: 1) characterize racial/ethnic differences in environmental endocrine disrupting chemicals and 2) systematically review literature on environmental endocrine disrupting chemicals and selected women's health outcomes in populations containing more than one racial/ethnic group. This review highlights the need for future work in determining whether higher exposures to some environmental endocrine disrupting chemicals might partly explain differences in women's reproductive health outcomes in these higher-exposure and high-risk groups.