What Is a Blighted Ovum?

A blighted ovum is the term used for when a fertilized egg attaches to the uterine wall, as in a normal pregnancy, but never goes on to develop into an embryo. While the gestational sac, which contains the egg, will continue to form and grow normally, the embryo itself will not. A pregnancy that results in a blighted ovum is also known as an anembryonic pregnancy and will ultimately end in a miscarriage, sometimes before a woman even knows she is pregnant.

In a normal pregnancy, the egg starts dividing within hours after being fertilized. Around 10 days later, the cells will have formed an embryo, which will implant itself in the uterus. From there, the placenta begins to develop and hormone levels begin to surge. With a blighted ovum, the cells never divide to the point of forming an embryo, or the embryo stops growing very shortly after it implants in the uterus.

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 via miscarriage.

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 one-off events and are unlikely to occur in future pregnancies. If you do experience more than one anembryonic pregnancy, your doctor may want to do tests to make sure there’s not an underlying cause of the problem, such as a hormone imbalance or genetic mutation. 

Symptoms of a blighted ovum may be non-existent and, as such, can be the underlying cause of what's known as a missed miscarriage. Alternatively, you may experience the typical symptoms of miscarriage, including:

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

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

Typically, your ob/gyn will do a routine ultrasound when you are roughly six weeks pregnant. In a normal pregnancy, an embryo should be visible at this time. With a blighted ovum, the gestational sac will be empty.

A transvaginal ultrasound, in which a wand is inserted directly into the vagina, may be used to confirm a blighted ovum if the results of a standard abdominal ultrasound are inconclusive.

If your doctor diagnoses a blighted ovum, he or she may recommend a procedure known as dilation and curettage (D&C). This surgical procedure involves the dilation of the cervix followed by 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.

Alternatively, a woman may prefer to wait for a natural miscarriage to occur. A natural miscarriage can sometimes take weeks and requires a doctor to monitor the process to ensure that all the tissue in the uterus has been appropriately expelled. If tissue remains in the uterus after the miscarriage, a D&C may still be required. If the tissue is not removed, infection can occur and lead to a potentially serious complication called a septic miscarriage.

Suffering a miscarriage as a result of a blighted ovum—or for any other reason—can be traumatic, even though there's nothing you or your partner did to cause it, nor is there anything you could have done to prevent it from happening. If you are struggling with coming to terms with the unwanted end of your pregnancy, you may want to consider seeing a counselor or joining an online support group. Keep in mind that the majority of women who have a miscarriage go on to have a healthy full-term pregnancy.