A blighted ovum occurs when a fertilized egg implants in the uterus but doesn't form an embryo. It is also referred to as an anembryonic (no embryo) pregnancy and is a leading cause of early pregnancy failure or miscarriage. Often it occurs so early that you don't even know you are pregnant.
A blighted ovum causes about 1 out of 2 miscarriages in the first trimester of pregnancy. A miscarriage is when a pregnancy ends on its own within the first 20 weeks.
When a woman becomes pregnant, the fertilized egg attaches to the uterine wall. At about five to six weeks of pregnancy, an embryo should be present. At about this time, the gestational sac (where the fetus grows) is about 18 millimeters wide. With a blighted ovum, the pregnancy sac forms and grows, but the embryo does not form. That's why a blighted ovum is also called an anembryonic pregnancy.
"When an ultrasound is performed after four to five weeks’ gestational age, measured from the first day of the last menstrual period, a fluid-filled sac can be seen within the uterine cavity, but no embryo is present," says Henry Dorn, MD, an obstetrics & gynecology specialist practicing in High Point, NC. A definite diagnosis can usually be made 11-14 days later if there's still no embryo.
What Causes a Blighted Ovum?
Miscarriages from a blighted ovum are often due to problems with chromosomes, the structures that carry genes. This may result from poor-quality sperm or egg or from abnormal cell division. In response, your body stops the pregnancy after detecting this abnormality.
It's important to understand that you have done nothing to cause this miscarriage, and you almost certainly could not have prevented it. For most women, a blighted ovum occurs only once.
"A confusing factor for patients is that the gestational sac generally contains placental tissue, which produces hormones that may cause typical pregnancy symptoms such as nausea, breast tenderness, tiredness, and so on,” says Dorn. Lab tests may show rising human chorionic gonadotropin (hCG) levels. This is the hormone made by cells that form in the placenta, which multiply quickly in early pregnancy.
Although with an anembryonic pregnancy, these hormone levels may rise somewhat slower than normal, those numbers alone can't ensure a diagnosis, Dorn says.
How common is it?
It's the main reason for miscarriages in the first trimester of a pregnancy.
"According to studies, anembryonic pregnancy may occur in as many as 15% of all pregnancies, and many go undetected in very early miscarriages, which occur before ultrasound is performed," Dorn says. "The occurrence rate rises with age and may be as high as 50% in women over 40 years old."
Risk factors for a blighted ovum
Researchers aren't sure why chromosomal problems happen as a fetus grows. But you're more likely to have an anembryonic pregnancy if you:
- Have had miscarriages in the past
- Are older than 35 when you get pregnant, when there's a higher chance of chromosomes being abnormal
- Have a health issue or an infection that's not been treated
"Anembryonic pregnancies account for about 50% of first-trimester miscarriages, and because they are common, may reoccur sometimes," says Dorn. "However, in most cases, they are a result of chromosomal anomalies arising from a specific sperm/egg pairing and do not represent underlying genetic disease."
Because you carry the same eggs in your body for your whole life (as compared to males who constantly make new sperm), there's more of a chance that defects in the DNA in an egg can happen over time. "That in part accounts for the rising miscarriage rate with advanced age," Dorn says. "The majority of healthy women, however, conceive normally following a miscarriage due to an anembryonic pregnancy, even in the cycle immediately following the miscarriage."
Since certain endocrine and autoimmune diseases also raise the chances of anembryonic pregnancy, further tests should be considered if it happens again, usually more than twice, he notes.
Signs of a Blighted Ovum
With a blighted ovum, you may experience signs of pregnancy. For example, you may have a positive pregnancy test or a missed period.
You may also have signs of a miscarriage, such as:
- Abdominal cramps
- Vaginal spotting or bleeding
- A period that is heavier than usual
If you're experiencing any of these signs or symptoms, you may be having a miscarriage. But not all bleeding in the first trimester ends in miscarriage. So, be sure to see your doctor right away if you have any of these signs.
How Long Can You Carry a Blighted Ovum?
It varies. Sometimes, a miscarriage can happen a few days after a pregnancy test is positive. Other times, the placenta keeps growing and making hormones. This can happen 7-12 weeks into the pregnancy. At this point, your body realizes an embryo isn't forming, and your uterus sheds the tissue it's prepared.
Diagnosing a Blighted Ovum
If you thought you had a normal pregnancy, you're not alone; many women with a blighted ovum think so because their levels of human chorionic gonadotropin (hCG) may increase. The placenta makes this hormone after implantation. With a blighted ovum, hCG levels can continue to rise because the placenta may grow for a brief time, even without an embryo.
For this reason, an ultrasound test is usually needed to diagnose a blighted ovum — to confirm that the pregnancy sac is empty.
Blighted Ovum Treatment
If you have been diagnosed with a blighted ovum, discuss with your doctor what to do next. Some women have a dilation and curretage (D&C). This surgery involves dilating the cervix and removing the contents of the uterus. Because a D&C immediately removes any remaining tissue, it may help you with mental and physical closure. It may also be helpful if you want a pathologist to examine tissues to confirm the reason for the miscarriage.
Another option may be to use a medication such as misoprostol on an outpatient basis. But it may take several days for your body to expel all tissue. With this medication, you may have more bleeding and side effects. With both options, you may have pain or cramping that can be treated.
Other women prefer to avoid medical management or surgery. They choose to let their body pass the tissue by itself. This is mainly a personal decision, but discuss it with your doctor.
After a miscarriage, your doctor may recommend that you wait at least one to three menstrual cycles before trying to conceive again.
Recovery
It can take anywhere from a week to a month to physically recover from a blighted ovum. After you have a miscarriage or a D&C, you'll have some cramping for up to a week. You might have bleeding for a few weeks, but it'll slowly get lighter until it completely stops. It's key to know that heavy exercise or activity can cause more bleeding.
It might take longer, up to six weeks, until the hormones leave your body and you have a period.
A miscarriage, including one from a blighted ovum, can cause sadness or grief. You might feel confused as to what happened, or feel let down if you'd been excited. Ask your doctor or midwife for self-care suggestions and support resources. Don't keep the loss to yourself. Tell your family and friends how you're feeling so they can support you.
Takeaways
A blighted ovum, also known as an anembryonic pregnancy, is very common.
It happens when an egg is fertilized and a placenta begins to form, but an embryo doesn't form.
It happens early in the pregnancy, often before you know about it. Most people go on to have normal pregnancies after having an anembryonic pregnancy. The chance of having one increases with age.
Blighted Ovum FAQs
How long does it take to pass a blighted ovum?
If you don't have a D&C, your body will realize there's a problem with the pregnancy and empty the uterus within 7-12 weeks.
When can I get pregnant again after a blighted ovum?
Waiting through at least two menstrual cycles before trying for another pregnancy is commonly advised after a miscarriage of any kind. Some practitioners prefer you wait for three cycles.
What does a blighted ovum look like?
An ultrasound will show an empty gestational sac.
Can a hormonal imbalance cause a blighted ovum?
Yes, hormone imbalances, such as your progesterone levels being too low, can cause a blighted ovum.
How to avoid an anembryonic pregnancy
Having a blighted ovum usually has nothing to do with your health. However, it's always a good idea to make efforts to stay healthy, including limiting alcohol and caffeine and not smoking.
