Background Diet is the main source of environmental heavy metal exposure. Previous studies suggest that heavy metal exposure during pregnancy can have adverse effects on the mother and developing fetus, and prenatal diet is the main source of exposure to these potentially toxic heavy metals.

Objective To investigate the effects of diet during pregnancy on the concentrations of five heavy metals (lead, mercury, cadmium, chromium, and arsenic) in whole blood of pregnant women.

Methods A total of 252 healthy pregnant women who were registered in a hospital in Wuxi were included in the survey. A self-made questionnaire was distributed to collect their basic information, pregnancy situation, and dietary information during pregnancy (including intake of grains, vegetables, fruits, meat, aquatic products, and dairy products), and the levels of lead, mercury, cadmium, chromium, and arsenic in whole blood of mid-pregnancy were detected by inductively coupled plasma mass spectrometry (ICP-MS). Spearman rank correlation was used to investigate the correlation between various heavy metal elements in whole blood, and logistic regression was used to explore the effects of diet during pregnancy on the concentrations of heavy metal elements in whole blood.

Results In this study, the average age of pregnant women was (29.13±3.93) years old. Nearly half (46.83%) of pregnant women consumed rice 8 times a week, and approximately 36.11% of all pregnant women consumed dairy products 4-7 times a week. Over two thirds (68.26%) of pregnant women consumed livestock meat ≥4 times a week, 54.76% consumed fruits 8 times a week, 60.32% consumed fresh vegetables 8 times a week, and 68.25% rarely (<1 time per week) consumed salad. About 80% of pregnant women hardly consumed (<1 time per week) fried and barbecued foods. The median concentrations (P₂₅, P₇₅) of lead, mercury, cadmium, chromium, and arsenic in whole blood of pregnant women were 9.10 (7.04, 11.62), 1.06 (0.74, 1.52), 0.54 (0.36, 0.76), 0.97 (0.60, 1.52), and 1.02 (0.66, 1.79) μg·L⁻¹, respectively. Except for arsenic (90.87%), the detection rates of the other four heavy metals were all 100%. The concentrations of lead in whole blood of pregnant women were positively correlated with the concentrations of mercury (r=0.19), cadmium (r=0.26), and chromium (r=0.23) (P<0.01). The logistic regression analysis results showed that the intake of rice, livestock meat, fish, and shrimp/crab/shellfish during pregnancy was positively associated with the whole blood mercury concentration OR (95%CI): 1.40 (1.07, 1.82), 1.61 (1.21, 2.15), 1.69 (1.26, 2.25), 1.63 (1.22, 2.18).

Conclusion These research findings suggest that pregnant women in Wuxi may have mercury exposure issues associated with high consumption of rice, livestock meat, and aquatic products (fish and shrimp/crab/ shellfish). However, no correlation is found between dietary habits and other heavy metals such as lead, cadmium, chromium, and arsenic.