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expert reaction to study investigating flame retardants and pregnancies in women undergoing IVF

Publishing in Environmental Health Perspectives, researchers looked at organophosphate flame retardants (PFRs), studying the urinary concentrations of their metabolites along with outcomes of IVF treatement. They reported a negative association between the concentration of certain types of PFR metabolites in the urine of these women and the proportion of successful outcomes of IVF.


Prof Warren Foster, Professor of Obstetrics & Gynaecology, McMaster University, said:

“The authors explored potential associations between urinary metabolite concentrations of organophosphate flame retardants and pregnancy outcomes of women undergoing IVF.  The study included 211 women and generated 297 IVF cycles. Thus some women contributed more than once cycle data and urine sample for data analysis. Briefly there were five metabolite concentrations and the sum of all metabolites assessed across at least 11 IVF outcome measures.

“This is a very interesting study that reveals potential statistical associations between the sum of the PFR and some isolated metabolites with some outcome measures. A weakness of this study is the failure to account for contribution of samples from more than one IVF cycle to the data (at least that I was able to discern from a quick read of the paper) and the absence of any control for multiple comparisons. Another potential limitation to the study is that there is no insight into when the exposures occurred and their relationship with the outcome measures being studied. Moreover, there is no information on duration of infertility and other interventions if any that have been pursued by the women or their male partners. Finally, the study participants have experience difficulty in achieving pregnancy for a period of time (usually greater than a year) before undergoing medical evaluation and care. It is unclear how this process and underlying health problems may contribute or modify exposures. Furthermore, the above issues together with a 60% recruitment success may also limit translation of results to the wider community of women attempting to achieve pregnancy many of whom will not have trouble conceiving.

“Despite the above noted limitations the data reveal statistical associations between PFR metabolites in the urine and some IVF outcome measures. However, these data do not establish risk or causal linkages. Regardless, the data are important scientifically and should prompt further study into the reproductive and developmental hazards associated with exposure to PFRs. Further studies will be required to determine PFR compound-related adverse effects and to define the relevant mechanisms of action so that health risks can be determined.”

Prof Allan Pacey, Professor of Andrology, University of Sheffield, said:

“There has been much interest in whether a class of chemicals present in the human environment called endocrine disruptors are a threat to human fertility. In this study the authors examined whether metabolites of flame retardant chemicals in the urine of women undergoing IVF are correlated with various outcome measures of IVF.

“In brief, the study seems well conducted and the analysis shows that as the urine concentration of some of the metabolites increases there is a corresponding decrease in the likelihood of fertilisation happening, or the probability of the embryo implanting, or the chances of the baby being born.

“On the face of it, this data seems fairly convincing and support the idea that there is a link between a woman’s exposure to these flame retardant chemicals and her chances of getting pregnant. However, the data does not prove it (it only describes an association) and consequently I would urge caution in how this study is interpreted.

“For example, it is not clear if this effect would be seen in couples who are not undergoing IVF, or whether this association is particular to this group of people. Also, it is not possible to say whether this association is present in all parts of the world where laws and use of these chemicals may be different. Finally, we should be sensitive to the fact that the urinary metabolite concentration of these chemicals in this study could be a surrogate marker for another aspect of the woman’s lifestyle that is actually causing the effect observed.

“Ultimately, we need to keep our lives safe from fire and so before men and women undergoing IVF throw away their yoga mats, I think we need a bit more data in larger populations and in various parts of the world. We also need some more details about the likely mechanism by which these chemicals could be causing such an effect.

“Until then, I think any couples about to embark on IVF should try and be as healthy as possible and of course not delay seeking medical help if they suspect they have a fertility problem.”


Prof Richard Anderson, Professor of Clinical Reproductive Science, MRC Centre for Reproductive Health, University of Edinburgh, said:

“There is growing concern that the chemicals we are all exposed to may have an impact on fertility, but direct evidence of impact in men and women has often been limited. This carefully conducted study analysed chemicals from flame retardants in urine from women having IVF, and found that the chemicals were detected in most women.  Worryingly, higher concentrations of these chemicals were associated with substantial reductions in the success of IVF, with a lower chance of having a baby.  Studying couples having IVF is a powerful way of carrying out analyses such as this, as it allows each of the steps in conception and pregnancy to be examined, which isn’t possible in natural conception.

“While this study doesn’t prove that these chemicals are the cause of the lower success rate, it provides a firm basis for further experiments to investigate them.  It also provides strong support for the need to regulate our exposure to chemicals and test their potential impact on fertility”


* ‘Urinary Concentrations of Organophosphate Flame Retardant Metabolites and Pregnancy Outcomes among Women Undergoing in Vitro Fertilization’ by Carignan et al. was published in Environmental Health Perspectives  on Friday 25 August.


Declared interests

Prof Richard Anderson: “I am a member of the FIGO (International Federation of Gynaecology and Obstetrics) ‘Reproductive and Developmental Environmental Health Working Group. No other conflicts.”

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