Lab case 34 – Interpretation

1. Give 3 differentials:

Ectopic pregnancy

Abortion – threatened, inevitable, incomplete, complete

Ruptured corpus luteum cyst

Others – less likely

2. Priorities:

Calm, professional approach, reassurance to patient

Attend to any immediate resuscitation issues – ABC approach


Careful rapid assessment to rule out life threats – history, examination, +/- early ultrasound (FAST vs formal)

Early Gynaecology assessment in ED if indicated

3. History:

Bleeding – amount, appearance, clots, menorrhagia, metrorhagia, dycfunctional uterine bleeding, post coital

Reproductive history – menarche, menstrual, pregnancy, last normal menstrual period, contraception

Sexual –  current, previous, barrier protection

Risk factors for ectopic pregnancy – previous ectopic pregnancy, tubal surgery, PID, abortion/TOP, infertility treatment, cigarette smoking, endometriosis, uterotubal abnormalities. Weaker – young age of sexual activity, multiple sexual partners, vaginal douching

Associated features – trauma, bleeding diathesis, urinary symptoms, syncope, blood group

4. Discriminatory zone:

By correlating the serum beta-hCG values to the size of an intrauterine gestational sac, a value can be chosen that corresponds to the threshold of visualization of the sac. If the beta-hCG is above this value, a sac must be seen, and if it is not (pregnancy of unknown location), aggressive steps should be taken to determine whether the pregnancy is abnormal or ectopic.

The most reliable ultrasonographic criteria for diagnosing ectopic pregnancy are based on the appearance of the uterus in the presence of a positive pregnancy test. The absence of an intrauterine sac signifies ectopic pregnancy, whereas its presence indicates intrauterine gestation. These criteria cannot be applied when serum pregnancy tests are used unless the serum human chorionic gonadotropin (hCG) level at which the sac of an intrauterine pregnancy becomes visible on ultrasound is known, because these tests are far more sensitive and identify pregnancy at an earlier stage than does sonar.

The hCG level that distinguishes patients with intrauterine pregnancies in whom a gestational sac can be seen from those in whom it cannot be seen is designated the discriminatory hCG zone. This zone is greater than 5000 mIU/ml for abdominal ultrasound and more than 1500 mIU/ml for transvaginal ultrasound. The absence of an intrauterine sac in conjunction with hCG values above this level signifies ectopic pregnancy. However, the absence of an intrauterine sac has no diagnostic significance when associated with hCG values below the discriminatory zone.

An intrauterine sac associated with hCG levels above the discriminatory zone reliably indicates an intrauterine pregnancy, but at hCG values below the zone, it is suggestive of an abnormal pregnancy-either a missed abortion or an ectopic gestation.