Urinary bisphenol A concentrations and association with in vitro fertilization outcomes among women from a fertility clinic

Abstract

Study question: Are urinary BPA concentrations associated with in vitro fertilization (IVF) outcomes among women attending an academic fertility center?

Summary answer: Urinary BPA concentrations were not associated with adverse reproductive and pregnancy outcomes among women from a fertility clinic.

What is known already: Bisphenol A (BPA), an endocrine disruptor, is detected in the urine of most Americans. Although animal studies have demonstrated that BPA reduces female fertility through effects on the ovarian follicle and uterus, data from human populations are scarce and equivocal.

Study design, size and duration: This prospective cohort study between 2004 and 2012 at the Massachusetts General Hospital Fertility Center included 256 women (n = 375 IVF cycles) who provided up to two urine samples prior to oocyte retrieval (total N = 673).

Participants/materials, settings, methods: Study participants were women enrolled in the Environment and Reproductive Health (EARTH) Study. Intermediate and clinical end-points of IVF treatments were abstracted from electronic medical records. We used generalized linear mixed models with random intercepts to evaluate the association between urinary BPA concentrations and IVF outcomes adjusted by age, race, body mass index, smoking status and infertility diagnosis.

Main results and the role of chance: The specific gravity-adjusted geometric mean of BPA was 1.87 µg/l, which is comparable to that for female participants in the National Health and Nutrition Examination Survey, 2011-2012. Urinary BPA concentrations were not associated with endometrial wall thickness, peak estradiol levels, proportion of high quality embryos or fertilization rates. Furthermore, there were no associations between urinary BPA concentrations and implantation, clinical pregnancy or live birth rates per initiated cycle or per embryo transfer. Although we did not find any associations between urinary BPA concentrations and IVF outcomes, the relation between BPA and endometrial wall thickness was modified by age. Younger women (<37 years old) had thicker endometrial thickness across increasing quartiles of urinary BPA concentrations, while older women (≥37 years old) had thinner endometrial thickness across increasing quartiles of urinary BPA concentrations.

Limitations, reasons for caution: Limitations to this study include a possible misclassification of BPA exposure and difficulties in extrapolating the findings to the general population.

Wider implications of the findings: Data on the relation between urinary BPA concentrations and reproductive outcomes remain scarce and additional research is needed to clarify its role in human reproduction.

Study funding/competing interests: This work was supported by NIH grants R01ES022955, R01ES009718 and R01ES000002 from the National Institute of Environmental Health Sciences (NIEHS) and grant T32DK00770316 from the National Institute of Child Health and Human Development (NICHD). None of the authors has any conflicts of interest to declare. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

Keywords: IVF outcomes; bisphenol A; endocrine disruptor; epidemiology; reproductive health.

© The Author 2015. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Figures

Figure 1

Adjusted rates (95% CI) in clinical outcomes per initiated cycle according to specific gravity adjusted urinary BPA concentrations (μg/l). Models are adjusted for age (continuous), BMI (continuous), smoking status (never and ever), race (white and others) and infertility diagnosis (male, female and unexplained). Tests for trend were performed using the median concentration of urinary BPA in each quartile as a continuous variable in the model. Implantation was defined as a serum β-hCG level >6 mIU/ml typically measured 17 days (range 15–20 days) after oocyte retrieval, clinical pregnancy as the presence of an intrauterine pregnancy confirmed by ultrasound and live birth as the birth of a neonate on or after 24 weeks gestation. Medians of each quartile of urinary BPA concentrations (μg/l) are presented.