A fertilized egg is like a seed that goes through a series of complicated and wonderful processes before it finally grows into a healthy baby. “Embryonic abortion is different from miscarriage in the middle and late stages of pregnancy, in that the development of the embryo stops before it is formed. The main clinical manifestations are menopause, loss of pregnancy response, vaginal bleeding, and ultrasound examination, which usually shows irregularity in the shape of the gestational sac, the absence of a germ or the presence of a germ without a heartbeat, or the withering of the germ. There are many causes of embryonic arrest. The specific reasons for fetal arrest are not necessarily the same for each pregnant woman. The most common reasons are as follows: 1. Factors of the embryo itself Some important tissues and organs do not develop normally in the early stages of embryonic development, which is a natural elimination, i.e. “survival of the fittest, elimination of the inferior”. If an embryo with chromosomal abnormalities is aborted, the pregnancy product is sometimes an empty gestational sac or a degenerated embryo, and even if the pregnancy is full term, the fetus will be found to have deformities or functional defects after birth. Therefore, prenatal diagnosis is needed to prevent the birth of chromosomally affected children. The reproductive medicine experts at the First Hospital of Lanzhou University Specialized Hospital of Reproductive Medicine remind that especially for women aged >35 years, there are also adverse environmental influences such as toxic chemicals, radiation, high temperature, radiation, etc. that can cause chromosomal abnormalities in the embryo and lead to abnormal embryo development. 2, placental dysplasia The fetus grows and develops in the mother’s body mainly through the placenta to transport the mother’s nutrients and oxygen to the fetus, if the placenta is dysplasia or disease, the fetus will not get nutrients and oxygen and stop growing. Maternal factors Pregnant women suffer from the following systemic diseases, such as severe diabetes, hypertension, heart disease, viral hepatitis, severe anemia, chronic nephritis or severe malnutrition, especially vitamin deficiency, as well as mercury, lead and alcohol poisoning, which cause abnormal embryo development. Pregnant women infected with rubella virus, cytomegalovirus, simple scar virus, Toxoplasma gondii or suffering from influenza, typhoid fever, pneumonia, etc. can cause miscarriage in early pregnancy. This is because the pathogens after maternal infection can cause damage to the chorionic villi and capillary endothelium through blood circulation and destroy the placental barrier, and the pathogens enter the fetus leading to embryonic arrest, miscarriage or fetal malformation. Reproductive organ diseases such as uterine malformation, uterine fibroids or uterine adhesions, the internal environment of the uterus and the overall environment of the uterus may have an impact on the embryo. The internal environment is the endometrium, if it is too thin or too thick, it will affect the implantation. 4. Abnormal maternal immune system There is a complex and special immunological relationship between the embryo or fetus and the mother, and this relationship keeps the embryo or fetus from being rejected in the mother’s body. Immunological maladjustment between the mother and the fetus can cause the mother to reject the fetus and prevent the development of the embryo, i.e. “immune rejection”. 5, reproductive endocrine factors Embryo implantation and continued development depend on the coordination of the endocrine system, in the early stages of pregnancy estrogen, progesterone, human chorionic gonadotropin and other three hormones dominate, and in the mother’s body hormone levels are coordinated with each other, if the mother’s own hormone levels are not enough to meet the needs of embryonic development, it may cause embryo abortion and miscarriage. The most common one is insufficient luteal function, i.e. insufficient progesterone level, which causes delayed endometrial development and short luteal phase, thus affecting the planting of fertilized eggs or early pregnancy miscarriage. 6, external adverse factors Adverse factors also play an important role in the development of the fetus: such as trauma, excessive fatigue, mental stimulation, taking drugs that affect the development of the embryo, exposure to toxic chemicals, poor quality decoration materials, exposure to radiation or large amounts of electromagnetic radiation, etc.. There are also smoking, alcohol, coffee and drugs that affect the early embryonic development.