Possible causes of fetal arrest at 9 weeks of pregnancy include chromosomal abnormalities, maternal factors, paternal factors and environmental factors, and some unexplained fetal arrest. 1. Chromosomal abnormalities: chromosomal abnormalities include numerical abnormalities and structural abnormalities, with chromosomal numerical abnormalities being the most common. 2. Maternal factors: (1) Abnormalities of reproductive organs: for example, the mother suffers from uterine fibroids, which can cause fetal blood supply to decrease and cause fetal arrest. (2) Systemic diseases: hyperemesis gravidarum, cardiovascular diseases, etc. make the small arteries of the whole body spasm, and the embryo’s blood supply is abnormal, leading to fetal arrest. (3) Bad habits and strong stress: surgery, abdominal impact, excessive smoking, alcoholism, drug abuse, etc., can lead to fetal arrest. (4) Endocrine abnormalities: female luteal insufficiency and other endocrine abnormalities lead to fetal arrest. (5) Infections: Intrauterine infections, especially in early pregnancy, can lead to fetal arrest. (6) Abnormal immune function: the embryo belongs to allogeneic transplantation, and the immune maladaptation between mother and fetus can cause the rejection of the fetus by the mother. (3) Fathers’ factors: the decline in the quality of the father’s sperm is one of the reasons for the embryo’s cessation of development. 4. Environmental factors: excessive exposure to radiation, such as X-rays, and excessive exposure to chemicals, such as benzene, can lead to fetal arrest. There are many reasons for fetal arrest in early pregnancy, so it is recommended to have a systematic examination to clarify the cause and standardize the treatment according to the cause.