Causes and Diagnosis of a Blighted Ovum

Pregnancy may appear normal as embryo fails to develop

Pregnant woman having ultrasound scan
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A blighted ovum, also known as an anembryonic pregnancy, is a type of miscarriage in which the fertilized egg never develops or stops developing once it attaches to the uterine wall. While the cells of the gestational sac will continue form and grow normally, the embryo itself will not.

A blighted ovum occurs during the first trimester and often before a woman even knows that she’s pregnant.

Causes

A blighted ovum is most often the result of chromosomal abnormalities in the fertilized egg.

This may be due to abnormal cell division or a poor-quality egg or sperm that makes the pregnancy non-viable from the start. When the body recognizes this, it will discontinue the pregnancy.

There is no evidence that a blighted ovum is caused by anything the mother does or does not do. Most cases of blighted ovum are a once-off event, never happening again.

Symptoms

Symptoms of a blighted ovum may be non-existent and, as such, be considered a missed miscarriage. At other times, the woman may experience typical symptoms of miscarriages, including:

  • Vaginal spotting or bleeding
  • Abdominal cramps
  • Blood clots or grayish tissue passing from the vagina

Diagnosis

In cases of a blighted ovum, early blood tests will often indicate that the pregnancy is progressing just fine. This is because levels of human chorionic gonadotropin (hCG), a hormone produced by the placenta, will continue to rise as the placenta develops even if an embryo is not present.

If a miscarriage is suspected, an ultrasound will typically be used to evaluate the pregnancy. If there is a blighted ovum, the gestational sac will be empty. (In a normal pregnancy, an embryo would be visible on an ultrasound by around six weeks.)

A transvaginal ultrasound, which is inserted directly into the vagina, may be used if the results of a regular abdominal ultrasound are inconclusive.

With that being said, doctors will often prefer to perform an abdominal study and request a follow-up 10 days later to see whether the pregnancy is developing.

Treatment

If a blighted ovum is diagnosed, the doctor may recommend a procedure called a dilation and curettage (D&C). This surgical procedure involves the dilation of the cervix and the removal of the contents of the uterus using a looped tool called a curette. Vacuum aspiration, in which excess tissue is removed by suction, may also be performed.

As a D&C removes all remnant a miscarriage, it may help some women get mental and physical closure following an understandably traumatic event.

Others may prefer to have a natural miscarriage. Women who choose this option often do so because they see closure as a process rather than an event. Unlike the immediacy of a D&C, a natural miscarriage can sometimes take weeks and requires a doctor to monitor the process to ensure all tissue has been appropriately expelled. If not, the infection can occur and lead to a potentially serious complication called a septic miscarriage.

In the event the uterus is not entirely cleared, a D&C may still be required.

Sources:

DeCherney, A.; Goodwin, T.; Nathan, L.; and Laufer, N. (2012) Current Diagnosis and Treatment: Obstetrics and Gynecology (11th Edition). New York City: McGraw-Hill Education.

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