Are human chorionic gonadotropins (hCG) tests necessary if a miscarriage is likely?

From the Guidelines

HCG tests are not always necessary if a miscarriage is likely, and a diagnosis can often be made based on clinical signs, ultrasound, and possibly a single HCG measurement. When a miscarriage is suspected, symptoms such as vaginal bleeding, cramping, and passage of tissue are typically present, and an ultrasound can help confirm the diagnosis. Serial HCG measurements, taken 48-72 hours apart, can be helpful in cases where the diagnosis is unclear, as they can show if pregnancy hormone levels are rising or falling 1. However, in a complete miscarriage where all pregnancy tissue has passed, HCG levels will gradually decrease to zero over days to weeks, and serial measurements may not be necessary.

Some studies have shown that serial HCG determinations have limited sensitivity and specificity in detecting ectopic pregnancy, with a sensitivity of 36% and specificity of 63% in one study 1. Additionally, transvaginal ultrasound can be useful in detecting ectopic pregnancy, but its sensitivity is limited when serum HCG levels are less than 1,000 mIU/mL, with a sensitivity of 19% in one study 1.

In terms of management, the safest method of evacuation is suction dilation and curettage (D&C) under ultrasound control, and histological examination of the products of conception is essential to achieve a correct diagnosis 1. A single HCG measurement or serial measurements may be recommended to confirm that the miscarriage is complete and no further intervention is needed, but this should be determined on a case-by-case basis, taking into account the individual patient's symptoms and clinical presentation.

Key points to consider include:

• Clinical signs and symptoms, such as vaginal bleeding and cramping, can often diagnose a miscarriage
• Ultrasound can help confirm the diagnosis
• Serial HCG measurements can be helpful in unclear cases, but may not always be necessary
• Histological examination of the products of conception is essential to achieve a correct diagnosis
• Suction dilation and curettage (D&C) under ultrasound control is the safest method of evacuation.

From the Research

hCG Tests in Miscarriage

• hCG tests can be used to confirm a successful medically induced abortion in early pregnancy, but should be used as supplements to clinical assessments 2
• The diagnosis of miscarriage is made with ultrasonography and, when ultrasonography is not available or is nondiagnostic, with measurement of beta subunit of human chorionic gonadotropin levels 3
• Serial serum hCG levels can be measured to predict complete abortion after medical induction, with a significant difference in daily decrements of hCG between ectopic pregnancies and miscarriages 4

Utility of hCG Monitoring

• The percentage change in total βhCG levels (%ΔβhCG) can be used to predict treatment outcomes following intravaginal misoprostol for missed miscarriage before 13 weeks 5
• A %ΔβhCG calculation over one week can reliably predict treatment outcomes after medical management of missed miscarriage, with a %ΔβhCG > 87% predicting no sac at TVUS and a %ΔβhCG > 94.5% predicting no surgery on clinical criteria 5

hCG Supplementation

• hCG has been used to prevent subsequent miscarriages after previous recurrent miscarriages, with a Cochrane database systematic review indicating that hCG seems to prevent further miscarriages 6
• However, the use of hCG supplementation is empiric and a new trial is indicated to compare recombinant hCG to urinary hCG and to placebo, with stratification for prognostic factors and correction for fetal chromosomal aberrations 6