Question
What is a missed miscarriage?
Last reviewed: September 2012
Expert Answer
Kim Mackenzie-Morris
Midwife sonographer and expert on scans.
A missed miscarriage, also called a silent miscarriage, can happen in any pregnancy. After conception, a fertilised egg (ovum) implants in your uterus (womb). Sadly, it's then that something goes wrong, and the pregnancy doesn't continue.
It may be that an embryo didn't develop at all and the pregnancy sac is empty, which is called a blighted ovum. Or it may be that an embryo started to grow, but failed to progress.
It's called a missed miscarriage because you won't realise that anything has gone wrong. You may not have had any of the usual signs of miscarriage, such as pain or bleeding. Your body may still be giving you signals that you are pregnant, though if your hormone levels are falling, those signs may lessen slightly. Your breasts may feel less tender, or you may find your pregnancy sickness has stopped sooner than expected.
The first time you are aware that anything is wrong may be when you have your first ultrasound scan. This is when you may be told either that the pregnancy sac is empty, or that the embryo has no heartbeat.
The news is bound to come as a shock, and you may find it hard to accept. Give yourself time to come to terms with it. Be reassured that most women go on to have successful pregnancies after a missed miscarriage.
Why does a missed miscarriage happen?
It usually happens because something went wrong in early pregnancy. Perhaps the embryo had the wrong number of chromosomes. At the moment of conception, when the sperm meets the egg, 23 chromosomes from each parent should meet, to make 46 in total.
Or perhaps a piece of a chromosome was missing, or was duplicated. This means the genetic material carried on the chromosomes weren't right for a baby to develop.
In a missed miscarriage, either the embryo doesn't develop, or it doesn't get very far, and the heartbeat stops. Occasionally it happens later, perhaps at eight weeks or 10 weeks, or even further on.
In later pregnancy, missed miscarriages may be due to an infection such as parvovirus or rubella. If your doctor thinks this may be cause, she will offer you a blood test for toxoplasmosis, rubella, cytomegalovirus and herpes simplex (TORCH). This will look for infections.
If during your ultrasound the sonographer thinks you may have suffered a missed miscarriage, a second sonographer will need to confirm the diagnosis. A diagnosis of miscarriage can only be confirmed if the pregnancy sac is more than 25mm (1in), with no baby seen. A baby that's still present must measure more than 7mm (0.3in) for your sonographer to be sure.
What will happen after the diagnosis?
You may decide to let nature take its course, as you will eventually miscarry. Or you may decide to have a minor operation called an evacuation of retained products of conception (ERPC). This operation will remove any pregnancy tissues from your uterus.
Your obstetrician will carry out the ERPC under a general anaesthetic, normally as a day procedure. You don't have to decide immediately what you'd prefer to do. You may need some time to think about it.
If you've had a miscarriage, it's natural to be anxious that it could happen again. But most women go on to have a successful pregnancy the next time around. Your doctor may recommend an early scan to reassure you. If it is not offered where you live, and you are very worried, your GP can request a scan.
Try to wait until you are more than six weeks, or better still, eight weeks pregnant, to avoid the uncertainty that very early scans may bring.
For more support and information about miscarriage, contact The Miscarriage Association.
