A blighted ovum is a type of very early miscarriage that happens when a fertilized egg never develops into an embryo or an embryo stops growing shortly after implantation.
Because it occurs within just a few weeks of ovulation and fertilization, many women aren't even aware that they were pregnant in the first place.
If you get a negative pregnancy test several days after a positive result, or if you’re diagnosed with an early miscarriage after an ultrasound, it’s natural to feel confused and upset. It can be reassuring to learn about the causes of a blighted ovum, especially since the odds remain very good of having a healthy pregnancy in the future.
What is a blighted ovum?
A blighted ovum, also known as an anembryonic pregnancy, occurs when something goes wrong shortly after conception. After an egg is fertilized and implants in the uterus, it begins to develop a placenta but not an embryo.
In a normal pregnancy, a sperm fertilizes an egg shortly after ovulation. Within hours, this fertilized egg starts dividing and eventually forms an embryo. Implantation spurs the placenta to start developing and hormone levels (including hCG, which is detected on a home pregnancy test) to rise. The embryo keeps growing and can appear as a speck on an ultrasound by around weeks 5 to 6 of pregnancy.
Doctors can diagnose a blighted ovum using an ultrasound starting at around week 7 of pregnancy. Imaging will show a smaller than normal and empty gestational sac without an embryo.
What causes a blighted ovum?
Most early miscarriages are due to chromosomal abnormalities. Research suggests that more than two-thirds of blighted ovum miscarriages involve genetic abnormalities. Maybe the fertilized egg had an extra chromosome or was missing a chromosome. That means it just didn’t have the right mix of genetic material to continue developing.
More About Pregnancy Miscarriages
Ultimately, a blighted ovum is the biological end of a pregnancy that’s not going quite right. That means there’s nothing you or your partner did to cause it, and there isn’t anything you could have done to prevent it from happening.
Symptoms of blighted ovum
A blighted ovum feels similar to a normal pregnancy at first. That’s because the body senses something has implanted in the uterus and produces hormones (including hCG) that cause early pregnancy symptoms. Many women with an anembryonic pregnancy still get a positive pregnancy test and experience symptoms like morning sickness, sore breasts and bloating.
When the fertilized egg fails to develop into an embryo, hCG levels begin to drop and pregnancy symptoms will begin to disappear. At this point it’s possible to experience signs of miscarriage, like bleeding and cramping.
Symptoms of blighted ovum may include:
- Heavy bleeding. Light bleeding and spotting can be normal early in pregnancy. You should see your health care practitioner if you have heavier bleeding that’s similar to your period.
- Severe cramping. Some cramping during pregnancy is also often normal, but always make sure to get cramps during pregnancy checked out if you’re concerned and especially if they’re accompanied by symptoms like bleeding or fever. Cramping can point to other pregnancy complications, including an ectopic pregnancy, that may require medical attention.
- An abnormal ultrasound. Your doctor will see a smaller gestational sac than expected that contains no embryo.
- Lower hCG levels. Research suggests that blood tests show lower levels of the pregnancy hormone hCG starting at about 6 to 8 weeks of pregnancy in anembryonic pregnancies.
A blighted ovum can only be diagnosed with an ultrasound, which reveals that a fertilized egg hasn’t developed into an embryo. An ultrasound also allows your practitioner to confirm that symptoms aren't caused by an ectopic pregnancy, or the implantation of a fertilized egg outside of the uterus (usually in a fallopian tube). Ectopic pregnancies cause similar symptoms to anembryonic pregnancies, but they require prompt medical treatment as they can result in serious nternal bleeding.
If you’re not sure about the first day of your last period and your doctor can’t spot an embryo at an ultrasound, your doctor may ask you to come back in a week for a follow-up ultrasound.
How common is a blighted ovum?
Blighted ovum is the most common cause of miscarriage. Experts estimate that blighted ovum accounts for about 50 percent of all miscarriages in the first trimester. About 15 percent of all pregnancies end in miscarriage before 13 weeks of pregnancy.
Keep in mind that like all types of miscarriages, blighted ovum miscarriages occur very early in pregnancy, so not all cases are diagnosed. That makes it difficult to come up with an exact count of how often this condition happens.
Treating a blighted ovum
If your doctor diagnoses a blighted ovum, he or she will likely consider the following treatment options:
- Expectant management. If your body recognizes that an embryo isn’t developing, it will expel the contents of your uterus with bleeding similar to a heavy period. Doctors often initially recommend waiting a few days to a week to see whether your body passes the anembryonic pregnancy naturally.
- Medication. If the hormones an implanted embryo produces cause the uterus to sustain the pregnancy, your healthcare practitioner may prescribe a medication that spurs the uterus to clear its contents.
- Surgery. Your doctor might also recommend a brief surgical procedure known as dilation and curettage (D&C) to empty the uterus.
How will a blighted ovum affect my chances of getting pregnant again?
Any pregnancy loss, no matter how early, can be heartbreaking. Here’s the good news: The odds are good that you’ll go on to have a healthy pregnancy and baby.
Most women only have one miscarriage before going on to having a healthy baby; only about 1 percent have repeat miscarriages. And the method of treatment following the loss — waiting, drugs or surgical procedure — doesn’t affect your odds of conceiving later.
If you have repeated incidents of blighted ovum, your doctor will likely recommend testing to make sure there’s not an underlying cause of the problem, such as a hormonal imbalance or genetic condition.
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