A molar pregnancy can happen when something goes wrong in the early stages of fertilisation that means that the baby and placenta don’t develop properly. We don’t yet fully understand all the reasons but we do know that molar pregnancies are not caused by anything you or your partner have or haven’t done.
There are two main types of molar pregnancy
Complete molar pregnancy
The fertilised egg of a healthy pregnancy is made up of 23 chromosomes from the mother and 23 chromosomes from the father.
In a complete molar pregnancy, genetic material from the mother is lost at the time of fertilisation. The egg contains only 23 chromosomes from the father and no chromosomes from the mother at all. This means that there is no baby.
The placenta develops rapidly with abnormal cells that grow as cysts. These cysts grow in clusters and can be seen on ultrasound. They are referred to as a mole.
Partial molar pregnancy
In a partial molar pregnancy the egg has the usual 23 chromosomes from the mother but is fertilised by two sperm, each with 23 chromosomes which makes 69 chromosomes in total rather than the normal 46.
Some normal placental tissue forms among the abnormal cells and a baby may begin to develop[FM3] , but it will be genetically abnormal and unable to live beyond 3 months.
Symptoms of a molar pregnancy
In many cases there may be no signs of a molar pregnancy and it may go undetected until your routine ultrasound scan at 11-13 weeks.
However, if you’re pregnant, these symptoms can be a sign of molar pregnancy:
- Bleeding from the vagina which is dark and irregular
- Severe morning sickness
- Quicker growth around the tummy
- Some tummy pain
Factors that increase the risk
- If you’re younger than 20 or older than 35
- A previous history of molar pregnancy, particularly if you’ve had more than two
- A low intake of carotene (a form of vitamin A)
- Ovulatory disorders such as Polycystic Ovary Syndrome (PCOS)
- Living in or coming from certain areas – molar pregnancies are more common for women in Southeast Asia but we still don’t know why
Treatment for molar pregnancy
If a molar pregnancy is suspected, it is likely that you will be referred to a specialist centre to manage the condition.
An ultrasound scan and a blood test will be carried out to confirm the diagnosis.
Once diagnosed, it may be necessary to remove the abnormal cells with a surgical procedure under general anaesthetic. The procedure is sometimes called SMM (Surgical Management of Miscarriage) or D&C (Dilatation and Curettage) or ERPC (Evacuation of Retained Products of Conception.)
If you need surgery, you will be taken into a quiet room and the treatment options will be explained to you in detail.
After the treatment, you will experience bleeding that may continue for up to six weeks after surgery and may be heavy and red at first. Some of the cells removed during treatment will be sent to the laboratory for testing and your pregnancy hormones (hCGs: human chorionic gonadotropins) will be monitored for at least six months in case they do not return to normal. Around one in ten women see no reduction in pregnancy hormones, and suffer a condition called persistent gestational trophoblastic disease, which means that abnormal molar cells continue to grow inside the womb. Fortunately treatment is available.
Will I still be able to have a baby in the future?
Yes, you have every chance of going on to have a normal pregnancy next time. The risk of another molar pregnancy is only about 1-2 percent.
With treatment and routine follow-ups, a molar pregnancy shouldn’t cause any problem to your long-term physical health.
However, likely to have to wait a while after your pregnancy hormones return to normal before trying again. You’re advised to avoid pregnancy for six months from the end of treatment if the initial surgery is successful, or 12 months from the end of treatment if you had additional medical therapy.
How you may feel about a molar pregnancy
Whilst all miscarriages are distressing, a molar pregnancy is unusual in that it brings shocks and anxieties over many months. Waiting for confirmation that any abnormal molar cells are eliminated and your pregnancy hormones are returned to normal, can make you feel like you’re in limbo. You may feel unable to grieve properly for the loss of your pregnancy. The process of finding out how things are progressing stage by stage can feel like a series of blows and the wait to conceive again can be stressful.
It’s important you don’t feel alone in your sadness or anxiety. Remember that most patients with successfully treated molar pregnancies subsequently go on to conceive healthy babies without any problems.
It’s important you don’t feel alone in your sadness or anxiety. Remember that a molar pregnancy doesn’t impact on your future fertility and the vast majority of women go on to have a healthy pregnancy afterwards.
And for more information, help and support, visit molarpregnancy.co.uk
Letting your miscarriage happen naturally is also called ‘expectant management.’
If the medical option hasn’t been completely successful, or if you are bleeding heavily or have an infection, you may be advised to have surgery.
If you have a missed or incomplete miscarriage, you will be offered the option to take some medicine to help the miscarriage to get underway.
What do you say to someone who's just lost a baby, even if it was never and could never have been a baby?
Certainly not things like "maybe it was for the best" or "Maybe your not ready for another just yet".
I don’t think we spoke much; we just held hands and looked at each other every now and then with a worried smile, scared for each other and for ourselves.
I love midwifery and rarely take it personally that seemingly everyone in the world I meet has a baby, but this time I needed a few days off work.
- Royal College of Obstetricians and Gynaecologists, Management of gestational trophoblastic disease, guideline 38, London RCOG, 2010
- Trophoblastic Tumour Screening and Treatment Centre, Information for patients with molar pregnancies or choriocarcinoma, London Charing CrossHospital, 2013. Also available at: http://www.hmole-chorio.org.uk/index.html (accessed 22 April 2014)
ℹLast reviewed on August 1st, 2016. Next review date August 1st, 2019.