Approximately 25% of women with a clinically recognized pregnancy experience some vaginal bleeding, with nearly half of those resulting in miscarriage. However, if a normal heart rate can be identified with ultrasound, more than 85% will reach term. In addition, ultrasound identification of intrauterine pregnancy (IUP) makes the risk of concurrent ectopic pregnancy less than 1 in 4000. A yolk sac can be seen with a beta-hCG of approximately 1700, and is the earliest ultrasound marker of an IUP. Fetal heart motion is usually seen with beat-hCG levels of around 17,000. When a heartbeat is identified, M-mode ultrasound is used to measure fetal heart rate as demonstrated in Figure 20-3B (Houry and Abbott, 2006:2741).