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In Women Undergoing in Vitro Fertilisation, High Levels of Environmental Mercury Have Negative Impact on the Number of Oocytes Retrieved: Presented at ASRM

By Crina Frincu-Mallos, PhD

WASHINGTON, DC -- October 24, 2007 -- High levels of mercury present in hair analysis correlates with lower numbers of oocytes retrieved in women undergoing in vitro fertilisation (IVF), researchers reported here at the 63rd Annual Meeting of the American Society for Reproductive Medicine (ASRM).

Joseph O. Doyle, MD, Vincent Memorial Obstetrics and Gynecology Service, Massachusetts General Hospital, Boston, Massachusetts, United States, presented the preliminary results of this ongoing study here on October 16.

"Our [patient] population consists only of patients in the Boston area, so this study is looking at an East Coast population and their mercury levels," said Dr. Doyle.

Dr. Doyle and colleagues conducted their study to determine whether there is a correlation between hair mercury level, embryo quality, and early developmental outcomes of the infants among women presenting for initiation of fertility treatment at Massachusetts General Hospital.

For the prospective cohort study, the researchers collected proximal hair samples 3-cm in length and determined their total mercury content. They compared the mercury content of the study population with the national median and with levels determined to be safe by the Environmental Protection Agency (EPA).

"In our 46 patients," said Dr. Doyle, "we looked at different oocyte and embryo colony measures [such as] numbers of oocytes retrieved, number of mature oocytes, fertilisation rate, and embryo grades [1-5, 1 being the best] for days 2 and 3."

Statistical analysis was performed using linear mixed effects regression models. The patient population was stratified by maternal age as an internal control in the study.

"The first interesting thing that we saw was the fact that, while the national median for mercury levels is 0.2 ppm, over 44% of our [patient] population was over the EPA guidelines." The EPA reference dose is 1 ppm.

Furthermore, added Dr. Doyle, in 20% of study participants, the mercury level was double the level of the EPA reference. "So, we have a population with really high levels compared to the national levels of mercury," Dr. Doyle said.

Interestingly, the mercury levels had a significant negative impact on embryo cell count on days 2 and 3, he said. In all the other parameters analysed, the researchers found no significant association, he noted. Yet, he continued, "with the number of total immature oocytes, it was a negative correlation [with mercury levels], it just wasn't statistically significant."

Each 1-ppm increase in mercury resulted in an estimated 0.070 (P =.43) increase in day-2 score, a 0.105 (P =.29) increase in day-3 score, and a 0.215 (P =.13) increase in day-5 score, showing a trend in poor embryo quality correlated with high mercury levels.

"This is an ongoing study, and hopefully, with the addition of more patients, we would find statistical significance in some of these other variables," said Dr. Doyle, but right now, it appears there is a relationship between mercury concentration and poor embryo quality, looking at embryo cell count numbers at days 2 and 3."

"This doesn't mean 'go out and get your mercury levels checked', at this point we need to power the study adequately, so we can see all the effects that [high levels of mercury] has," commented Dr. Doyle.

He added, "We don't automatically want to blame this on seafood, which, according to the literature, is the main source of our mercury exposure. We have to balance the benefits we get from seafood, as far as omega-3s, selenium, minerals, against the [detrimental] impact [of mercury] on the embryo cell count numbers."

Talking about future plans, "our goal is to reach 100 patients and then take a new look at the data," concluded Dr. Doyle.

This study was supported by grants from the United States National Institute of Environmental Health Sciences, National Institutes of Health, and grant from the U.S. National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention.


[Presentation title: Environmental Exposure to Mercury and Early Developmental Endpoints Among Women Undergoing IVF Abstract P-600]

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