The incidence of abortion in artificial insemination of dairy cows is about 10%, and the incidence of abortion in embryo transfer is about 15%. The causes of abortion are divided into two categories: infectious abortion and non-infectious abortion. Infectious abortion is a symptom of an infectious disease, and most abortions are non-infectious abortions. The causes of non-infectious abortions include: nutritional abortion, traumatic abortion, toxic abortion, drug-induced abortion, and symptomatic abortion. According to the age of abortion and changes in the fetus, abortion can be divided into the following types, and the abortion of cows can also be checked by cattle B-ultrasound.

Hidden abortion, also known as early embryonic death, occurs in the first 1-2 months of pregnancy, accounting for about 25% of abortions. Early embryonic death can be identified using cattle B-ultrasound.

Premature delivery is the discharge of unchanged dead fetuses, which occurs in the middle and late stages of pregnancy. This is the most common type of abortion, accounting for about 49.8% of abortions. In the middle and late stages of pregnancy, cattle B-ultrasound is needed for regular inspections to see the condition of the fetus.

After the fetus dies, it is retained in the uterus. Due to the closure of the cervix, the water of the fetus is absorbed and mummified. Dead fetuses often occur in the 4th to 5th month of pregnancy, accounting for about 24% of miscarriages. Mummification is easy to judge on cattle B-ultrasound and can be basically confirmed.

After the fetus dies, due to the invasion of non-corrupt bacteria into the uterus, the soft tissue of the fetus is dissolved and lost, and the bones are retained in the uterus. The age of the dead fetus is similar to that of the dry fetus, accounting for about 0.9% of miscarriages.

After the fetus dies, due to the invasion of putrefactive bacteria into the uterus, the fetus is corrupted and decomposed, and a large amount of gas is produced to enlarge the fetus and cause dystocia. It is the most dangerous type of miscarriage, which is extremely rare in clinical practice, accounting for about 0.3% of miscarriages. This requires farmers to improve the nutritional level of pregnant cows in the process of raising dairy cows, carry out reasonable management, prohibit feeding corrupt, frozen feed and poisonous plants, not drinking ice water, prevent the occurrence of problems such as improper care during strenuous exercise and long-distance transportation, and need to use cattle B-ultrasound for frequent inspections.