The common causes of fetal arrest at five weeks’ gestation include embryonic factors, maternal factors, paternal factors, and the environment. 1. Embryonic factors: abnormalities in the number and structure of chromosomes in the embryo at the fifth week of pregnancy may cause the embryo to stop developing, or miscarriage. 2. Maternal factors: maternal factors include systemic diseases, genital abnormalities, endocrine abnormalities, and bad habits after pregnancy. (1) Systemic diseases: pregnant women suffering from severe infections, high fever, severe anemia or heart failure, thrombotic disease, chronic wasting disease, etc. may have embryonic arrest. (2) Abnormalities of the genitals: If the uterus develops abnormally, uterine fibroids, uterine adenomyosis and other abnormalities, all of them can affect the normal development of the embryo development, resulting in the cessation of embryo development or miscarriage. (3) Endocrine abnormalities: when pregnant women suffer from luteal insufficiency, polycystic ovary syndrome and other endocrine abnormalities, they can affect the development of the embryo, resulting in the cessation of embryonic development or miscarriage. (4) Bad habits after pregnancy: after pregnancy, pregnant women are often overworked, overstressed, anxious, depressed and other bad habits, which can cause the embryo to stop developing or miscarriage. (3) Father’s factor: Father’s sperm chromosome abnormality, or sperm development deformity, etc. may cause the embryo to stop developing. 4. Environmental factors: Frequent exposure to chemicals or gases, such as arsenic, lead, formaldehyde, etc., during the fifth week of pregnancy can cause embryonic arrest or miscarriage. There may be other reasons why the embryo stops developing during the fifth week of pregnancy, so you need to go to the hospital and terminate the pregnancy in time to avoid affecting your health.