A blood test for serum progesterone and serum HCG does not require fasting. Clinically, serum progesterone and serum HCG are often used to identify normal intrauterine pregnancy from ectopic pregnancy. In normal intrauterine pregnancy, blood progesterone value is greater than 25 ng/mL. If the serum progesterone value is less than 25 ng/mL, consider the possibility of ectopic pregnancy or miscarriage. Consider an intrauterine pregnancy if the blood HCG value is less than 10,000 U/L and rises 1-fold every 2 days. If the serum HCG value does not rise or rises very little, consider the possibility of ectopic pregnancy or miscarriage. The gestational sac is visible on B-mode ultrasound at 4-5 weeks of gestation and is approximately 2-5 mm in diameter, with a serum HCG value of 1500-3000 U/L. When the yolk sac is visible on B-mode ultrasound at 5-6 weeks of gestation, the serum HCG value is 5000 U/L. When the fetal heartbeat is visible on B-mode ultrasound at 6-7 weeks of gestation, and the diameter of the head and buttocks is greater than 5 mm, the serum HCG value is 15,000 U/L.