Objective To investigate the antagonism of zinc to mercury caused toxicity in mothers and fetuses and its anti-oxidation mechanism. Methods According to the levels of maternal blood mercury at middle and late pregnancy, 90 pregnant women were divided equally into the case group, the treatment group, and the control group. The levels of maternal blood mercury and zinc, and neonatal growth and development indexes of three groups were compared. The levels of glutathione peroxidase (GSH-PX), superoxidase dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) in placenta were detected by lipid peroxidation kit. Results The level of maternal blood mercury at late pregnancy of the treatment group was lower than that of the case group, while the level of zinc was higher than that of the case group and the difference was statistically significant (P<0.05). The level of maternal blood mercury of the treatment group at late pregnancy was lower than that

at middle pregnancy, while the level of zinc was higher than that at middle pregnancy and the difference was also statistically significant (P<0.05). The head circumference, crown-heel length, and birth weight of neonates of the case group were significantly lower than those of the treatment group in which the data were better (P<0.05). The levels of GSH-PX, SOD, and CAT in placenta of the treatment group were higher than those of the case group, but lower than those of the control group. The level of MDA in placenta of the treatment group was lower than that of the case group, but higher than that of the control group, and the differences were statistically significant (P<0.05). Conclusion Zinc supplement during pregnancy can antagonize mercury caused toxicity in mothers and fetuses. Antioxidant effect of zinc may be one of the important mechanisms.