From the Guidelines
No, hCG is not always positive with ectopic pregnancy. While human chorionic gonadotropin (hCG) is typically present in most ectopic pregnancies, there are cases where hCG levels may be undetectable or below the threshold of standard pregnancy tests, especially in very early ectopic pregnancies or in cases where the pregnancy has already begun to resolve spontaneously.
Key Points to Consider
- hCG levels in ectopic pregnancies often rise more slowly and irregularly compared to normal intrauterine pregnancies, as the implanted embryo outside the uterus doesn't develop the same robust placental connection that would produce normal hCG levels 1.
- Doctors typically monitor hCG levels over 48-hour intervals, looking for the expected doubling pattern seen in viable intrauterine pregnancies.
- An abnormal rise in hCG (less than 53% increase over 48 hours) may suggest an ectopic pregnancy, but clinical symptoms, ultrasound findings, and other diagnostic methods are essential for accurate diagnosis since hCG patterns alone are not definitive.
- The absence of an intrauterine pregnancy when the b-hCG level is >3,000 mIU/mL should be strongly suggestive (but not diagnostic) of an ectopic pregnancy, as suggested by Doubilet et al 1.
Diagnostic Approach
- Transvaginal ultrasound (TVUS) is currently considered the single best diagnostic modality to assess for ectopic pregnancy, with a high specificity for adnexal findings suggestive of ectopic pregnancy, including the classic “tubal ring” 1.
- TVUS as a screening test for ectopic pregnancy demonstrated a 99% sensitivity and 84% specificity in a prospective study of 1,427 patients with b-hCG levels >1,500 IU/L 1.
- A meta-analysis of 14 studies with 12,101 patients with ectopic pregnancy showed a positive likelihood ratio of 111 for the finding of adnexal mass without an intrauterine pregnancy on TVUS, making TVUS the single best diagnostic modality for evaluating patients with suspected ectopic pregnancy 1.
From the Research
Ectopic Pregnancy and hCG Levels
- Ectopic pregnancy occurs when a fertilized ovum implants outside of the uterine cavity, and its diagnosis can be challenging due to non-specific symptoms such as abdominal pain and vaginal bleeding 2, 3.
- The current standard for ectopic pregnancy diagnosis includes ultrasound imaging and β-human chorionic gonadotropin (β-hCG) monitoring 3.
- hCG is a glycoprotein hormone composed of 2 dissimilar subunits, alpha and beta, joined non-covalently, and the free beta-subunit is the principal immuno-reactive agent in pregnancy serum samples 4.
hCG Levels in Ectopic Pregnancy
- Improved diagnostic methods using hCG levels in combination with transvaginal ultrasound have led to earlier detection rates, subsequent treatment, and a reduction in mortality resulting from ectopic pregnancies 4.
- The diagnosis of ectopic pregnancy can be made with ultrasound visualization of a yolk sac and/or embryo in the adnexa, but most ectopic pregnancies do not reach this stage, and patient symptoms combined with serial ultrasonography and trends in beta human chorionic gonadotropin levels are used to make the diagnosis 2.
- Pregnancy of unknown location refers to a transient state in which a pregnancy test is positive but ultrasonography shows neither intrauterine nor ectopic pregnancy, and serial beta human chorionic gonadotropin levels, serial ultrasonography, and, at times, uterine aspiration can be used to arrive at a definitive diagnosis 2.
Treatment of Ectopic Pregnancy
- Treatment of diagnosed ectopic pregnancy includes medical management with intramuscular methotrexate, surgical management via salpingostomy or salpingectomy, and, in rare cases, expectant management 2, 5.
- The choice of treatment depends on various factors, including the patient's reproductive desire, gestational age, serum β-hCG levels, and fetal cardiac activity presence 6, 5.
- Conservative treatment without any need of further surgical intervention may be sufficient for full recovery with the preservation of reproductive capacity in some cases of ectopic pregnancy 6.