What does blighted ovum mean?

A blighted ovum is an early pregnancy in which the pregnancy sac forms in the womb but no baby develops inside it. The medical name is anembryonic pregnancy, meaning "without an embryo", and it is a type of miscarriage.

Australia's Pregnancy, Birth and Baby service puts it simply: "a sac (a fluid-filled pouch in the womb) and placenta grow, but there is no embryo (developing baby)." The pregnancy "will eventually lead to a miscarriage, usually in the first trimester". In the US, ACOG's definition of early pregnancy loss includes a pregnancy in the womb "with either an empty gestational sac or a gestational sac containing an embryo or fetus without fetal heart activity".

You may also hear "early pregnancy loss" or, when it is found on a scan before any bleeding, a missed miscarriage, a term that also covers an embryo that has stopped developing.

Blighted ovum symptoms

Often there are none. The NHS says that sometimes "you may have no symptoms and you'll only find out you've had a miscarriage at a pregnancy scan. This is called a missed miscarriage." When there are symptoms, Pregnancy, Birth and Baby lists pain in the lower tummy and bleeding from the vagina.

It is often found at an early scan you expected to be routine. Pregnancy, Birth and Baby acknowledges this "can be distressing if you were expecting good news".

How a blighted ovum is diagnosed

By a transvaginal (internal) ultrasound scan, and usually not on one scan alone. In the UK, NICE guideline NG126 tells sonographers to look first for a heartbeat, then measure the embryo if there is one, and only measure the sac if no embryo (fetal pole) can be seen. For an empty sac:

Transvaginal scan finding	Mean sac diameter	What NICE says should happen
Empty sac, no fetal pole	under 25.0 mm	A second scan at least 7 days later before any diagnosis. Further scans may be needed.
Empty sac, no fetal pole	25.0 mm or more	A second opinion and/or a second scan at least 7 days later before diagnosis.
Sac measured only on a tummy scan	any size	Record the size and repeat the scan at least 14 days later.

For an embryo with no heartbeat, NICE uses a crown–rump length of 7.0 mm as the equivalent cut-off.

Why one scan is not enough

Because a pregnancy can be earlier than your dates suggest. NICE tells clinicians to explain that "the diagnosis of miscarriage using 1 ultrasound scan cannot be guaranteed to be 100% accurate and there is a small chance that the diagnosis may be incorrect, particularly at very early gestational ages." The wait is hard, but it is a safeguard: ACOG warns that treating before the diagnosis is confirmed risks "interruption of a normal pregnancy".

Blighted ovum and hCG levels

Blood tests for the pregnancy hormone hCG support the picture but do not decide it. ACOG says ultrasound is the preferred way to check that a pregnancy in the womb is developing, and that "several ultrasound exams and hCG tests may be needed to confirm that a pregnancy has been lost". A positive pregnancy test does not rule out a blighted ovum.

What causes a blighted ovum?

Usually a random problem with the chromosomes. Pregnancy, Birth and Baby says the cells that would form the baby "do not grow as expected", that this "often happens because of random chromosome (gene) problems", and that "it is not caused by anything that you have done." The RCOG says there is no evidence that stress causes miscarriage.

Early loss is common: ACOG says it happens in about 10 of every 100 known pregnancies.

Your options: waiting, medicine or a procedure

Once the diagnosis is confirmed, the NHS says you will usually be offered options, depending on your symptoms and how many weeks pregnant you are.

Waiting (expectant management). NICE recommends 7 to 14 days of waiting as the first option, unless you are at higher risk of heavy bleeding (for example, late in the first trimester), have had a previous traumatic pregnancy experience, have a bleeding disorder or cannot have a transfusion, or have signs of infection. The RCOG says it works for about 50 in 100 women.
Medicine (medical management). NICE says this should be offered if waiting is not acceptable to you. The RCOG puts success at about 85 in 100. ACOG notes one large US trial found lower success for anembryonic pregnancies (81%) than other losses, but that a later analysis found only active bleeding and never having given birth were strong predictors of success, so medicine is a reasonable option for any type.
A procedure (surgical management). NICE says you should, where suitable, be offered a choice of manual vacuum aspiration under local anaesthetic in a clinic, or surgery in theatre under general anaesthetic. The RCOG says it succeeds in about 95 in 100 women.

After waiting or medicine, NICE says you should be given a urine pregnancy test to do at home 3 weeks later, and to return if it is positive. If your blood group is RhD negative and you were at least 12 weeks pregnant, the NHS says you may be offered an anti-D injection.

When to get help now

The NHS says to call 999 if you are pregnant, have vaginal bleeding and:

severe pain in your tummy that stops you doing daily tasks or focusing
pain in your shoulder
you feel sick, faint or dizzy, or lose consciousness
heavy bleeding, soaking a period pad soon after putting it on

In Australia, Pregnancy, Birth and Baby says to call triple zero (000) or go to an emergency department for heavy bleeding, severe tummy pain, dizziness or fainting, or fever or chills. In the US, ACOG says to contact your ob-gyn right away if bleeding is heavy or comes with cramping pain.

After a blighted ovum

The NHS says bleeding or spotting can last up to 2 weeks and your period can take up to 8 weeks to return; our cycle after miscarriage calculator estimates when. Pregnancy, Birth and Baby and the RCOG both advise pads rather than tampons.

"There is no right way to feel after a miscarriage," Pregnancy, Birth and Baby says. The NHS says counselling may be offered, or you can ask your GP or pregnancy unit. Our UK baby loss support guide lists leave rights and organisations, and when your partner has a miscarriage is written for partners.

The NHS says most women who have had a miscarriage go on to have a successful pregnancy, and the RCOG says one or two early miscarriages do not put you at higher risk of another. See trying to conceive after a miscarriage for timing. The NHS says to see a GP after 3 or more miscarriages.

Frequently asked questions

What is a blighted ovum?

A blighted ovum, or anembryonic pregnancy, is an early pregnancy where the sac and placenta tissue grow but no embryo develops. It is a type of miscarriage and usually happens because of a random chromosome problem. It is not caused by anything you did, and it usually does not affect future pregnancies.

What does a blighted ovum look like on an ultrasound?

An empty pregnancy sac in the womb with no embryo (fetal pole) inside. Because a very early pregnancy can look similar, NICE recommends a repeat scan at least 7 days later when the sac measures under 25.0 mm, and a second opinion or repeat scan when it is larger, before a diagnosis is made.

How long does it take to miscarry a blighted ovum naturally?

The NHS says waiting for a miscarriage to happen naturally usually takes about 2 weeks, but can take longer. NICE recommends 7 to 14 days of waiting as the first option in most cases, with a repeat scan if bleeding and pain have not started, and medicine or a procedure available if you would rather not wait.

Can you have a successful pregnancy after a blighted ovum?

Yes. Pregnancy, Birth and Baby says an anembryonic pregnancy usually does not affect your chances of having a baby in future and that your next pregnancy is likely to be normal. The RCOG says one or two early miscarriages do not raise your risk of another.

Blighted Ovum (Anembryonic Pregnancy): What It Means