From the Guidelines
An ectopic pregnancy will typically show a positive result on a urine human chorionic gonadotropin (hCG) screen, but a positive test alone cannot distinguish between a normal intrauterine pregnancy and an ectopic pregnancy. The urine pregnancy test detects the presence of hCG hormone, which is produced by the placenta after implantation occurs, regardless of whether the implantation is in the uterus (normal pregnancy) or outside the uterus (ectopic pregnancy) 1. However, it's essential to understand that the hCG levels in ectopic pregnancies may sometimes be lower than in normal pregnancies at the same gestational age, but they are still usually high enough to trigger a positive result on a urine test.
Key Considerations
- A positive pregnancy test alone is not sufficient to diagnose an ectopic pregnancy, and additional tests such as blood hCG measurements and transvaginal ultrasound are typically required for diagnosis 1.
- If you have a positive pregnancy test and experience symptoms such as severe pelvic or abdominal pain, vaginal bleeding, shoulder pain, or dizziness, you should seek immediate medical attention as these could indicate an ectopic pregnancy, which is a medical emergency requiring prompt treatment.
- Ultrasound correlated with serum human chorionic gonadotropin (hCG) levels and clinical presentation can usually differentiate causes of first-trimester bleeding, including normal intrauterine pregnancy, nonviable intrauterine pregnancy, gestational trophoblastic disease, and ectopic pregnancy 1.
Diagnostic Approach
- The diagnostic approach to suspected ectopic pregnancy typically involves a combination of clinical evaluation, urine or serum hCG testing, and ultrasound imaging 1.
- Transvaginal ultrasound is the preferred imaging modality for evaluating suspected ectopic pregnancy, as it can provide more detailed images of the reproductive organs than transabdominal ultrasound 1.
From the Research
Ectopic Pregnancy and Urine hCG Screen
- An ectopic pregnancy occurs when a fertilized ovum implants outside of the uterine cavity 2.
- 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 2.
- Patient symptoms combined with serial ultrasonography and trends in beta human chorionic gonadotropin (hCG) levels are used to make the diagnosis 2.
- Although rare, ectopic pregnancy has even been demonstrated in women with negative urine β-hCG tests or low serum β-hCG levels 3.
Urine hCG Screen and Ectopic Pregnancy
- A urine hCG screen may not always detect an ectopic pregnancy, especially in early stages or with low serum β-hCG levels 3.
- Serial β-hCG levels, serial ultrasonography, and uterine aspiration can be used to arrive at a definitive diagnosis of ectopic pregnancy 2.
- The utility of endometrial sampling for the diagnosis of pregnancy location has been described, allowing a significant proportion of women to avoid methotrexate by diagnosing failing intrauterine pregnancies instead 4.
Diagnostic Challenges
- Ectopic pregnancy is a difficult diagnosis and may be missed on initial evaluation 3.
- Patients with early ectopic pregnancy may have positive ultrasound findings with serum β-hCG levels under a defined discriminatory zone (DZ), while some patients with an early viable intrauterine pregnancy may have no visible findings on initial ultrasound, but have serum β-hCG levels well above the DZ 3.
- Understanding the myths surrounding ectopic pregnancy may help emergency physicians consider it, even when patient risk factors, symptoms, or laboratory or imaging studies do not initially or easily define the diagnosis 3.