At 23 weeks pregnant, a fetoprotein of 251 nanograms per milliliter is normal. Fetoprotein 251 nanograms per milliliter at 23 weeks of pregnancy is normal. It is a dangerous condition if it exceeds 800 ng per milliliter because it starts to rise from 12 to 14 weeks of pregnancy and reaches a peak of 380 to 500 ng per milliliter in the 32nd to 34th week of pregnancy. Alpha-fetoprotein is a specific protein synthesized in the liver of the fetus. It is elevated during pregnancy, but does not exceed 500 ng per milliliter and gradually returns to normal after delivery. If the value exceeds the normal range, it may be due to liver disease or abnormal development of the fetus, which may lead to high alpha-fetoprotein. If the value of alpha-fetoprotein is higher than the normal level, the patient should have further diagnosis in time and be treated by a professional doctor.