There are two units of progesterone: one is the large unit ng/L; one is the small unit nmol/L, and the ratio between the two is 3.18. 40 days of pregnancy is six weeks, and the range of progesterone values is 32.6-139.9 nmol/L. Low progesterone during pregnancy is likely to cause uterine contractions, which can lead to miscarriage, and can also cause fetal arrest, so you need to take a reasonable supplement of progesterone under the guidance of a doctor, and also pay attention to observing the symptoms of abdominal pain and vaginal bleeding. symptoms of vaginal bleeding. If bleeding occurs, consider the aura of miscarriage, in the ultrasound to rule out ectopic pregnancy, you can take progesterone or injection of progesterone to protect the fetus, at the same time to supplement vitamin E. It is best to bed rest, do not exercise strenuously, strengthen the diet and nutrition, relaxation, more lean meat, eggs and other foods, keep the bowel movement, to prevent constipation.