The normal value of HCG at 4 weeks of pregnancy usually ranges from 100-10000 IU/L and is related to the early and late ovulation and the early and late formation of the fertilized egg. If ovulation is early, the earlier the fertilized egg is formed, the higher the blood HCG is, and if ovulation is late, the later the fertilized egg is formed, the lower the blood HCG is. The value of HCG increases exponentially with the week of gestation and is proportional to the amount of trophoblast secretion. In clinical practice, HCG is usually retested every other day to determine the condition of the embryo. If the HCG value tends to double, it indicates that the embryonic cells are well developed and there is a greater chance of intrauterine pregnancy. Sometimes HCG may also be negative at 4 weeks of pregnancy and you need to wait for 1-2 weeks before the HCG value may increase, so you cannot tell whether it is a preterm miscarriage or ectopic pregnancy by a single HCG result. However, ectopic pregnancy is highly suspected if the blood HCG exceeds 2500-3000 U/L at 4 weeks of pregnancy and there is no intrauterine gestational sac in the ultrasound examination.