Biomarkers of metal toxicity in embryos in the general population

With the development of industrialization, public exposure to toxic metals could occur everywhere, eventually affecting individuals' reproductive systems and even embryos and leading to early pregnancy loss. The aim of the study was to determine the profile of toxic metal levels in pregnant women in the general population and to identify biomarkers for metal toxicity in embryos.

A case-control study with pregnant women was conducted at Peking Union Medical College Hospital in 2016-2018. Women who experienced spontaneous abortion within 12 weeks of gestation comprised the case group, and women with pregnancies showing fetal cardiac activity who requested an induced abortion almost simultaneously were included in the control group. Blood and urine specimen were tested for concentrations of cadmium, chromium, selenium, arsenic, and mercury.

A total of 195 patients were enrolled, with 95 in the case group and 100 in the control group. Significant differences in gravidity, parity, history of miscarriage, mean blood cadmium levels, and mean urine chromium levels were present between the two groups (P1 = 0.013, P2 = 0.000, P3 = 0.000, P4 = 0.002, P5 = 0.046); the odds ratios in the spontaneous abortion with blood cadmium >0.4 µg/L, urine chromium >2 µg/L, gravity <3, parity <2, and history of miscarriage >1 compared with the induced abortion group were 1.26 (1.09, 1.85), 1.56 (1.23, 2.53), 1.39 (1.17, 1.98), 1.72 (1.21, 4.62), and 1.18 (1.06, 1.65), with P-values of 0.003, 0.031, 0.003, 0.247, and 0.001, respectively.

Blood cadmium and urine chromium levels are two possible biomarkers of toxic metal embryotoxicity in the general population, which means that in the general population, blood cadmium >0.4 µg/L or urine chromium >2 µg/L might indicate an increased risk of spontaneous abortion.