Short summary

This intervention study seeks to determine whether diet counseling can reduce mercury exposure in Danish pregnant women.
Pregnant women who are referred to Odense University Hospital (OUH) receive written information about the project when invited for ultrasound scan in early pregnancy. The participants are asked to fill in a short questionnaire, they receive dietary advice, both orally and in writing in order to minimize exposure to mercury, and a hair sample is obtained for mercury analysis.
At least 4 months later, the questionnaire is repeated, a new hair sample taken and the results are compared.

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Rationale

Inorganic mercury is naturally occurring in nature. Microorganisms in the water can convert it into methylmercury which can easily pass cell membranes. Methylmercury is neurotoxic and can cross the blood-brain barrier and the placenta which makes this exposure particularly problematic for pregnant women. The major source of exposure to methylmercury is seafood, especially predatory fish. It is unclear to what extent Danish women are exposed to mercury and the effect of any intervention.

The main risk of mercury exposure is damage to the nervous system, which already happens in the embryonic stage with the risk of slower learning and development in children. Studies have shown that such damage is likely to occur, even at very low concentrations of mercury.

Long-term exposure to mercury is best measured by analyzing a hair sample, since mercury binds to the keratin during the formation of the hair root. Mercury has a half-life in the body of about 45 days. As hair grows at the rate of about 1 cm. per month, it is possible to measure the recent exposure.

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Description of the cohort

Only adult and legally competent pregnant women are included in this study.

Women who eat fish more than 2 times a week are invited to participate. The women must be able to speak and understand Danish to participate in the study. The women must also have hair longer than 3 cm in order to participate.

Data and biological material

Mercury analysis of hair samples and questionnaire responses about fish intake and other sources of mercury exposure are included in this projects.

Also pregnancy parameters obtained from patient records (hemoglobin, pre-pregnancy BMI, weight gain in pregnancy) and obstetric and neonatal outcomes (sex, gestational age at birth, birth weight and length, maternal diabetes, preeclampsia) are included.

Collaborating researchers and departments

Department of Environmental Medicine, University of Southern Denmark

• Professor Philippe Grandjean, MD, DMSc

Department of Obstetrics and Gynaecology, Odense University Hospital

• Consultant and Chief Obstetrician Jan Steiner Jørgensen, MD, PhD

OPEN Odense Patient data Explorative Network, Odense University Hospital