Molar pregnancy: what it is, treatment and follow-up

A molar pregnancy is a rare kind of pregnancy loss, where a pregnancy doesn’t form properly from the start. Finding out can be very hard, and the follow-up can feel long.

What happens in a molar pregnancy

A molar pregnancy, also called a hydatidiform mole, starts at fertilisation, when the genetic material from the egg and sperm doesn’t combine in the usual way, so the pregnancy can’t develop into a baby. There are 2 types:

Complete molar pregnancy: a sperm fertilises an egg that has no genetic material from the mother. There’s no baby, only the cells that would normally form the placenta, growing in the wrong way.
Partial molar pregnancy: 2 sperm fertilise one egg, so there’s too much genetic material. Sometimes a baby begins to form, but it isn’t able to grow or survive.

A molar pregnancy isn’t cancer. It happens by chance, and it isn’t caused by anything you or your partner did or didn’t do. It won’t make it harder for you to get pregnant in future.

Signs

Often there are no symptoms beyond the usual pregnancy ones. When there are signs, they can include:

bleeding or a dark discharge from your vagina, sometimes with tiny fluid-filled cysts
being sick a lot (severe pregnancy sickness)
a bump that looks bigger than expected for your stage of pregnancy

How it’s diagnosed

A molar pregnancy is often found at a routine scan between 8 and 14 weeks. Sometimes it’s only found after a miscarriage, when the pregnancy tissue is checked in a laboratory. If it’s suspected, you may have:

a blood test for the pregnancy hormone hCG, which is usually higher than normal
an ultrasound scan
an appointment with a gynaecologist or an early pregnancy unit

Treatment

A molar pregnancy sometimes ends on its own as a miscarriage. If not, it’s usually removed with a procedure using gentle suction, normally under general anaesthetic, so you’re asleep. Most people go home the same day. Sometimes medicine is used instead.

Follow-up: checking your hCG

Afterwards, your doctor registers you with one of 3 UK specialist centres: Charing Cross Hospital in London, Weston Park Hospital in Sheffield, or Ninewells Hospital in Dundee. The centre runs your follow-up, but you may not need to go there.

Follow-up checks that your hCG level goes back to normal. You have regular blood or urine tests, often every 2 weeks. Blood tests are done at your GP surgery or local hospital, and urine samples can be sent from home using a kit from the centre.

How long it lasts depends on the type of molar pregnancy. After a partial molar pregnancy, it usually ends with a final check about 4 weeks after your hCG is back to normal. After a complete molar pregnancy, it usually lasts 6 months or more, depending on how quickly your level falls. Your centre can tell you what to expect.

Waiting before trying again

Use contraception throughout follow-up, and wait until your specialist team says it’s safe before trying for another pregnancy. A new pregnancy raises hCG too, which would hide whether any molar tissue was growing back. Ask your GP or specialist team which contraception suits you. You’ll usually be advised not to have a coil fitted until your hCG is back to normal.

If you do get pregnant during follow-up, tell your specialist team straight away.

If you need more treatment

Most people don’t. Sometimes, and more often after a complete molar pregnancy than a partial one, some molar cells stay in the womb and keep growing. This shows up as hCG that doesn’t fall as expected, which is what follow-up is there to spot.

Doctors may call this persistent trophoblastic disease, an invasive mole or gestational trophoblastic neoplasia (GTN). It’s treated as a rare type of cancer, but one that responds extremely well to treatment. This is usually chemotherapy at Charing Cross or Sheffield, and the cure rate is over 99%. If you’ve had chemotherapy, you’ll usually be advised to wait 12 months before trying for another pregnancy.

How you might feel

You may be grieving a pregnancy you’d hoped for while taking in an unfamiliar diagnosis and months of tests. Recovery can take time, physically and emotionally, and there are no right or wrong feelings. The NHS lists these sources of support:

Molar Pregnancy Support and Information: molarpregnancy.co.uk
Miscarriage UK: helpline 0303 003 6464, and a monthly online support group for people who’ve had a molar pregnancy
Tommy’s: free midwife helpline 0800 0147 800, Monday to Friday, 9am to 5pm
Charing Cross Hospital Trophoblast Disease Service: patient information and drop-in sessions

Sands also supports people after a molar pregnancy, on 0808 164 3332.

When to get help

If you’re pregnant and have any bleeding or dark discharge, or pain that’s severe, on one side, or not easing after resting for 30 to 60 minutes, or pain in the tip of your shoulder, contact your maternity unit or an early pregnancy unit straight away, or NHS 111 if you can’t reach them. If you haven’t seen a midwife yet, call NHS 111 or your GP surgery. Also call your midwife or GP for urgent advice if you’re being sick a lot, or your bump seems bigger than it should be.

During follow-up, contact your specialist centre or GP if you have bleeding that carries on for longer than expected after treatment, or any other symptoms that worry you.

Call 999 if bleeding is heavy (soaking a pad soon after putting it on), or comes with severe tummy or shoulder pain, or with feeling sick, faint or dizzy; and for sudden, severe tummy pain with feeling faint or dizzy, even without bleeding.

Questions people ask

Is a molar pregnancy a miscarriage?

It’s a type of pregnancy loss, and charities such as Miscarriage UK and Sands support people who’ve had one. Whatever you call it, it’s OK to grieve.

Is a molar pregnancy cancer?

No, a molar pregnancy isn’t cancer. If some cells are left behind and keep growing, this is treated as a rare type of cancer, but follow-up picks it up early and treatment cures over 99% of people.

Would a pregnancy test show a molar pregnancy?

A test will be positive, often strongly, because hCG is high, but it can’t tell you the pregnancy is molar. That needs a scan and blood tests.

How long after a molar pregnancy can I try again?

Once follow-up has finished and your specialist team says it’s safe, or usually 12 months after chemotherapy.