Blighted ovum: what is it, what causes it and will it happen again?

We explain what 'blighted ovum' means, what causes it, how it's treated – and how likely it is to happen in another pregnancy

heartbroken woman

Blighted ovum – literally “damaged egg” – is often called anembryonic pregnancy or early embryonic loss by doctors. All are terms used to describe what happens when a fertilised egg implants in the wall of your womb (uterus) but doesn’t develop any further after  that.

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A “gestational sac” forms to contain and protect the expected embryo but either the embryo doesn’t develop at all or it stops developing very early. Sometimes, when this is discovered, it is referred to as “an empty sac”.

When there is a blighted ovum, miscarriage is, sadly, inevitable. But the particularly gutting thing about blighted ovum is that the bleeding and pain that normally signal a miscarriage may not happen straightaway (or at all).

And because the gestational sac may also keep growing, your body may carry on releasing the pregnancy hormone human chorionic gonadtrophin (hCG) that turns pregnancy tests positive and causes those early pregnancy symptoms such as tender breasts and nausea.

If this is the case for you, you’re unlikely to know that anything’s gone wrong with your pregnancy. And when you do find out – most likely at your 1st ultrasound scan – it can (obviously) be a real shock.

What happens when you’re told you have a blighted ovum or empty sac?

If you go for an ultrasound scan and your sonographer detects an empty sac, what happens next depends on how big the gestational sac is. That’s because it can be hard to be sure of the diagnosis if the sac is still very small.

In the UK, according to the Royal Society of Obstetricians and Gynaecologists (RCOG) guidelines for ultrasound screening, a blighted ovum is not formally diagnosed until the gestational sac is at least 20mm long, and there’s no evidence of an embryo or yolk sac inside.

If the sac is smaller than 20mm, or you’re having a very early scan and the sac is smaller than expected for your pregnancy due date, then you’ll probably be asked to wait a week or 2 and then come back for a further scan.

This is to allow for the possibility that your pregnancy due date may be wrong and actually everything is developing just fine. But, of course, that means a long, anxious wait, as Candyapplemumdrum posted about on our MadeForMums Forum:

“I went for any early scan yesterday and I was 6 weeks pregnant. I got an internal scan which showed a 7mm gestational sac but nothing else – no yolk sac, no embryo, nothing. I’m booked for another scan next Friday and I’ll be 7+4. They said they wouldn’t do another one too soon. I want to give everything a chance to grow. Fingers crossed and another looooong week for me!”

If, however, the sac is 20mm long – either at your 1st or subsequent follow-up scans – and there’s no sign of an embryo, you will be diagnosed with blighted ovum.

If you are not in pain or bleeding and you seem otherwise in good health, your doctor may suggest something called “expectant management” – which basically means waiting for your miscarriage to happen without medical or surgical intervention – because, eventually, your body will realise you are not pregnant. However, this may take some time to happen.

If you can’t bear the idea of waiting, or if your doctor doesn’t advise it, you may be offered “medical management” (usually a pessary, inserted vaginally, containing a drug that should start or speed up the miscarriage process) or “surgical management“.

What causes blighted ovum?

The most common cause of blighted ovum is genetic, according to recent studies.

“Doctors think that a blighted ovum pregnancy happens because of an issue with the early development of the baby – for example, a chromosome error,” says Ruth Bender Atik from the Miscarriage Association.

“It is extremely unlikely to be caused by anything you or your partner did – or didn’t – do.”

Coping with miscarriage cause by blighted ovum

Losing a pregnancy through blighted ovum is – of course – every bit as upsetting as any other cause of miscarriage.

Some people may try to console you with the idea that there never really was a baby to lose but this usually isn’t helpful. If you had a blighted ovum, then your egg was fertilised and you were truly pregnant – even if only for a short time.

As Tommy’s Midwife Amina Hatia points out, “This is a pregnancy loss and, like all other early pregnancy losses and miscarriages, it can result in a unique form of grief.  Give yourself time and permission to grieve – it is important to recognise the emotional, as well as the physical, impact this can have on you.”

If you need to talk to someone…

Will it happen to me again?

It could do – because any pregnancy always carries a risk of miscarriage – but it’s unlikely.

“A blighted ovum is a chance event and most women go on to have a healthy pregnancy,” says Ruth Bender Atik.

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