At 85 days of pregnancy the fetus is almost formed, the placenta has formed, and fetal development is relatively stable, but stability is relative, not absolute. There is a possibility that the embryo will stop developing throughout the pregnancy. If there is a pre-thrombotic state in the middle or late stages of pregnancy it can lead to insufficient blood supply to the placenta, fetal developmental delay and death, and if the umbilical cord is too long or knotted during fetal development, it can also cause fetal death. If the patient has vaginal inflammatory diseases that are not treated in time, it can cause upward infection leading to uterine cavity infection and cause fetal death, or due to various viral microbial infections leading to uterine cavity infection and cause fetal death. In the middle and late stages of pregnancy, you need to do regular pregnancy checkups and pay attention to fetal movement, if you find abnormal fetal movement or abdominal pain or bleeding, you should go to the hospital in time.