can an ectopic pregnancy be missed on an ultrasound?

Diagnosing Ectopic Pregnancy With Ultrasound
By Krissi Danielsson
Updated on January 26, 2022
Medically reviewed by Brian Levine, MD, MS, FACOG
Fact checked
by Aaron Johnson
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Table of Contents

Definition
Symptoms
Diagnosis
Treatment

Ectopic pregnancy can be challenging to diagnose based on symptoms alone because symptoms may not always be obvious. Early diagnosis is essential, though, as an untreated ectopic pregnancy can result in a ruptured fallopian tube, resulting in serious complications for the pregnant person.1
What Is an Ectopic Pregnancy?

An ectopic pregnancy occurs when a fertilized egg implants outside of the uterus. More than 90% of ectopic pregnancies implant in the fallopian tube. For this reason, ectopic pregnancy is also sometimes referred to as a tubal pregnancy.2

Ectopic pregnancies occur in 1% to 2% of all pregnancies.3 When an ectopic pregnancy develops undetected for too long, it can become life-threatening for the pregnant person. The main risk is that the fallopian tube can rupture, which can cause severe internal bleeding.1 Doctors must perform emergency surgery if your fallopian tube ruptures.
Understanding Your First Trimester Ultrasound
Ectopic Pregnancy Symptoms

Symptoms of an ectopic pregnancy can be easy to miss. Often early signs mimic early pregnancy signs. Your doctor may suspect ectopic pregnancy if a pelvic exam reveals an abnormal lump in the tubal area or if you have unusual abdominal pain or tenderness.

Early symptoms of ectopic pregnancy may include:4

Vaginal bleeding
Cramping
Low back pain
Mild abdominal or pelvic pain

Always err on the side of caution and report any vaginal bleeding or pelvic pain to your doctor.

Symptoms of potential rupture may include:4

Sudden and severe abdominal or pelvic pain
Shoulder pain
Dizziness, fainting

A ruptured fallopian tube is a medical emergency. If you are pregnant and have severe abdominal or pelvic pain, shoulder pain, or dizziness, go to the emergency room or call 911.
What Are Normal hCG Levels During Pregnancy?
How an Ectopic Pregnancy Is Diagnosed

If your doctor suspects an ectopic pregnancy, they may run tests to confirm or rule it out. The diagnosis includes a combination of hCG level testing and ultrasound.
Blood Tests

Human chorionic gonadotropin (hCG) is a hormone found in a pregnant person’s blood and urine. In an uncomplicated, early pregnancy, hCG levels typically double every couple of days.

The hCG levels in an ectopic pregnancy often rise slower than usual, meaning they will not double every two to three days in early pregnancy. Slowly rising hCG levels may be the first clue that leads a doctor to investigate the possibility of tubal pregnancy.5

Slow-rising hCG can also occasionally occur in a viable pregnancy, but it can also indicate a first-trimester miscarriage.6 HCG levels on their own cannot confirm an ectopic pregnancy.
Ultrasound

Doctors can definitively diagnose an ectopic pregnancy when an ultrasound reveals the gestational sac or embryo outside of the uterus.7 If the ultrasound shows a gestational sac in the uterus, on the other hand, your doctor can rule out a tubal pregnancy. Studies have found that ultrasound as a diagnostic tool for ectopic pregnancies is reliable and accurate.8

Transvaginal ultrasound is recommended over abdominal ultrasound because it is far more sensitive in the early stages of pregnancy. Additionally, the angle is better for viewing a possible ectopic mass.9

Most often, an ectopic pregnancy develops in the fallopian tube. More rarely, it can grow in other surrounding organs, including the ovary, cervix, a cesarean scar, and the abdominal cavity.10

Frequently, the sac will never be visible at all on ultrasound in a tubal pregnancy.

When your doctor can not see a sac in the uterus or the surrounding region, it is called a "pregnancy of unknown location."7 This will require a decision to either carefully watch and follow-up with another ultrasound and monitoring hCG levels, or treatment for suspected ectopic pregnancy.9

An ultrasound can most accurately show a gestational sac between eight and 10 weeks. But, by halfway through the fifth week, an ultrasound should be able to identify a gestational sac if it is in the uterus.9
Ectopic Pregnancy Treatment

Ectopic pregnancies are not viable as a fetus cannot develop and thrive outside of the uterus. As a result, they are considered a type of pregnancy loss. But unlike early miscarriage, which may be allowed to proceed naturally and without intervention (known as expectant management), treatment for ectopic pregnancy typically involves medication or surgery. The type of treatment your doctor recommends will depend on several factors, including your risk of rupture and how far along you are in your pregnancy.

If your doctor confirms that your pregnancy is ectopic, but there is no sign of rupture, they may recommend treatment with a medication called methotrexate. Methotrexate stops cells from growing, which ends the pregnancy. The body then absorbs the cells over the next month and a half.11

If there is a significant risk that the ectopic pregnancy may rupture your fallopian tube, however, your doctor will likely recommend surgery. Sometimes your doctor can remove the pregnancy without removing the fallopian tube. Other times, they will need to remove the fallopian tube.12
A Word From Verywell

It can be heartbreaking to learn that a pregnancy is not viable, and with ectopic pregnancy, it's an experience that can further be intensified in the face of a possible medical emergency. Ectopic pregnancy can be life-threatening, so early diagnosis is essential. If you suspect you may be experiencing an ectopic pregnancy, call your doctor right away.