Beta-Human Chorionic Gonadotropin Levels and its Role in Ectopic Pregnancy Diagnosis

An ectopic pregnancy is when a fertilised egg implants and grows outside the main cavity of the uterus, usually in one of the fallopian tubes. Unfortunately, the pregnancy cannot be saved and can cause significant health risks to the mother. Where not detected promptly, this can lead to severe harm, such as loss of a fallopian tube, resulting in potential reduced future fertility.

Beta-hCG (bhCG) is a test which measures the level of human chorionic gonadotropin (hCG) in the blood, a key hormone marker which is usually indicative of a pregnancy. bhCG is a quantitative test which means that not only does it confirm whether this hormone is present but also the exact amounts. Where this level continues to rise following a suspected miscarriage or where an ultrasound scan cannot identify a failed intrauterine pregnancy (i.e., by visualisation of the yolk sac), this hormone may indicate an ectopic pregnancy.

Whilst a bhCG test is not always performed or necessary in routine pregnancies as many practitioners will use transvaginal ultrasound to see evidence of the gestational sac to confirm pregnancy, as this article will explore, bhCG should always be considered to rule out a suspicion of an ectopic pregnancy in certain circumstances.

Case study

A pregnant patient had been referred by their GP to hospital following a recent history of red vaginal spotting. An ultrasound was performed which could not identify a viable intrauterine pregnancy, and the team, in this instance made a diagnosis of an anembryonic pregnancy (where an embryo never develops or stops developing and is reabsorbed which leaves an empty gestational sac). Unfortunately, an ectopic pregnancy was missed.

This case demonstrates the real-world importance of not making the assumption that a pregnancy is a failing intrauterine pregnancy with an empty sac and not a pregnancy of unknown location. Therefore, missing the differential diagnosis of a potential ectopic pregnancy of unknown location (PUL). BhCG hormone levels should always be calculated to ensure an ectopic pregnancy is ruled out, especially where a yolk sac is not able to be visualised on the scan.

Recommendations to Improve Patient Safety and Clinical Standards:

• Sonographers should remain aware of the Guidelines on Management of Pregnancies of Unknown Location and Ectopic Pregnancies should be increased (https://www.nnuh.nhs.uk/publication/diagnosis-of-ectopic-pregnancy-and-pregnancy-of-unknown-location-pul-and-management-of-g3-v5/)

• A pregnancy of unknown location should not be ruled out until a yolk is seen on the ultrasound scans

• hCG levels should be measured and documented in chronological order and if hCG levels are increasing following the suspicion of a miscarriage, ectopic pregnancy must be considered and investigated appropriately. If ectopic pregnancy is highly likely, refer to Early Pregnancy Unit/A&E as this is a medical emergency.