“Early diagnosis of ectopic pregnancy requires a high index of suspicion. Risk factors include previous ectopic pregnancy, tubal sterilization, pelvic inflammatory disease, IUD use, and in utero exposure to diethylstilbestrol. The classic triad of missed menses, pain, and bleeding may not always be present.
In early pregnancies of less than 5 weeks gestation, serial hCG levels are helpful. Serum hCG levels double every 1.4-2 days. In a healthy pregnancy the level is expected to increase by at least 66% in 48 hours. Combining serial hCG levels with transvaginal ultrasonography is the best combination for evaluation of first-trimester problems.
Serum hCG levels correlate well with sonographic landmarks. At 5 weeks gestation in a normal pregnancy, serum hCG is > 1000 mIU/mL and a gestational sac can be visualized in the uterus. Serum hCG is > 2500 mIU /mL at 6 weeks and a yolk sac can be seen within the gestational sac. An hCG level of 5000 mIU/mL is compatible with visualization of a fetal pole. When the level is 17,000 mIU/mL, cardiac activity can be detected. Progesterone levels are also predictive of fetal outcome. A single level of 25 ng/mL or higher indicates a healthy pregnancy and excludes ectopic pregnancy with a sensitivity of 98 %. If the level is < 5 ng/mL, the pregnancy is nonviable. Assessment of fetal well-being is difficult if levels are in the intermediate range of 5-25 ng/mL.” ABFM