Patients with diagnosis of spontaneous abortion are enrolled in the cohort, in the cohort of patients who met the criteria, 3ml of whole blood intravenous and 5ml of urine were taken for heavy metal level examnation. Part of the villi tissue was sent for genetic testing, and the results were traced. In addition, about 10g of villi tissue was frozen for testing. Patients with normal genetic results of villi tissue will have villus samples go through oxidative stress level detection.

From May 1, 2019, patients with diagnosis of spontaneous abortion are enrolled in the cohort, exclusion criteria were: not long-term residents in Peking; Inconvenient for following up; Long-term of drug use; Cesarean section scar pregnancy and other high-risk pregnancy; Diagnosis of pregnancy beyond 12 weeks.

In the cohort of patients who met the criteria, 3ml of whole blood intravenous and 5ml of urine were taken on the day of admission for curettage and suction, and the levels of heavy metals were tested. Part of the villi tissue was sent for genetic testing, and the results were traced. In addition, about 10g of villi tissue was frozen for testing. Patients with normal genetic results of villi tissue will have villus samples go through oxidative stress level detection.

Inclusion Criteria:

1) the length of fetal bud is equal to or greater than 7 mm and there is no cardiac activity; 2) the maximum zh diameter of the pregnancy sac is equal to or greater than 25mm, and there is no fetal heart beat; 3) an embryo with no heartbeat at 2 weeks or more after ultrasound examination showing a pregnancy sac without yolk sac; 4) embryos without heartbeat for 11 days or longer after ultrasonography showed the yolk sac as a type pregnancy sac.

Exclusion Criteria:

not long-term residents in Peking; Inconvenient for following up; Long-term of drug use; Cesarean section scar pregnancy and other high-risk pregnancy; Diagnosis of pregnancy beyond 12 weeks.