About one in six women of childbearing age have difficulty conceiving or carrying a pregnancy to term. Although there has been a global increase in the use of assisted reproductive technologies (ART), the live birth success rate has remained virtually the same.
Study: Association between chemical mixtures and female fertility in women undergoing assisted reproduction in Sweden and Estonia. Image credit: ADragan / Shutterstock
Infertility is defined as the inability to conceive after twelve months of regular unprotected intercourse. It can be caused by male, female or male/female factors. Ovarian disorders are one of the common causes of infertility. With hormones playing a vital role in ovarian function, scientists have speculated that exposure to man-made chemicals that damage the endocrine system may induce infertility.
Several chemicals have been identified as endocrine disruptors (EDCs), which alter the functions of the endocrine system and harm the body or its offspring. EDCs, such as bisphenols, per- and polyfluoroalkyl substances (PFAS), and phthalates, are associated with fertility and fertility. These chemicals are commonly found in everyday products, including common household and personal care items.
It is imperative to determine how EDCs are associated with biomarkers of female fertility, such as the ovarian sensitivity index (OSI). OSI measures ovarian capacity by analyzing its response to exogenous follicle-stimulating hormone (FSH) stimulation during ART. ISO is closely related to live birth (LV) rates as it determines the remaining oocyte pool and the functional aspects of the ovaries. Therefore, TSO has been considered a good biomarker of female fertility and a predictor of ART success.
Although women are exposed to a complex mixture of several chemicals through environmental exposure, most studies have only analyzed the effect of individual chemicals on humans and not their mixed form. A recent study Environmental research The journal study sought to address this limitation and conducted an epidemiological study to examine the impact of a mixture of known and suspected EDCs on female fertility.
About the study
Follicular fluid was collected from 333 women in Sweden and Estonia to establish the association between the chemicals and female fertility. OSI was assessed, which served as an indicator of ovarian response, clinical pregnancy (CP), and LB of fresh and frozen embryo transfers.
A total of 59 chemicals were detected in the follicular fluid samples, along with three phthalate metabolites, di-2-ethylhexyl phthalate (DEHP) metabolites, six PFASs and one paraben, in over 90% of the cohort studied.
The current study evaluated parabens, phthalates and PFAS as potential EDCs interacting with the endocrine system via numerous biological mechanisms. An inverse correlation between certain chemical concentrations and TSO has been observed. For example, a significant association was determined between a high DEHP (Swedish cohort) and methylparaben (Estonian cohort) metabolite concentration and a lower OSI. This finding indicates that these chemicals have a strong possibility of interfering with ovarian sensitivity in women. The results documented in this study are in agreement with previous studies which reported that a higher molar sum of DEHP metabolites was associated with a lower number of basal antral follicles (bAFC), and a lower possibility of LB and clinical pregnancy (CP) after ART.
The underlying mechanisms associated with the inverse relationship between DEHP and fertility have been found to be inhibition of antral follicle growth through reduction in 17-beta estradiol (E2) production and impaired functioning. ovarian.
Strengths and limitations
One of the main strengths of this study is its methodology. For example, the analysis of two separate cohorts improved the generalizability of the results. The authors claimed that this study was the first to investigate the relationship between EDCs and OSIs.
The small cohort size is an important limitation of this study. In addition, the assessment of clinical outcomes of individuals exposed to particular chemicals and chemical mixtures was seriously hampered by the low numbers of PCs and LBs in the study cohort. Another limitation of this study is the lack of adjustment for confounding factors in all analyses.
Conclusions and future prospects
The present study revealed the adverse effects of various types of chemicals on women in the area of fertility. An inverse relationship between DEHP metabolites and female fertility has been observed. Other chemicals, such as methylparaben and possibly PFUnDA and PFOA, have been identified as being associated with female infertility through disruption of ovarian function.
In the future, further research will be needed to determine the association between serum/urine DEHP and CP/LB during embryo transfer and early pregnancy. Although previous studies have established an association between higher concentration of parabens, poorer embryo quality and lower CP/LB levels, the mechanism of action related to parabens has not been determined. Gonadotropin sensitivity is an under-researched OSI-related indicator of fertility that also needs to be investigated in the future.