Molar pregnancy

A molar pregnancy happens when a fertilised egg has too much, or too little, genetic material. Because of this, the egg cannot develop into a baby.

Molar pregnancies are very rare. Only 1 in 600 pregnancies will be a molar pregnancy.

A complete mole is a fertilised egg that has too little genetic material inside it. It usually happens when a single sperm fertilises an "empty" egg. This egg has no genetic material in it, so a baby cannot develop. Instead, clusters of abnormal cells grow in your womb, and this is called molar tissue.

A complete molar pregnancy will still give you a positive pregnancy test and pregnancy symptoms. That's because of the molar tissue.

A partial mole is a fertilised egg that has too much genetic material inside. This can happen because:

• 2 sperm have fertilised a normal egg
• an egg had double the normal amount of genetic material before being fertilised

With so much genetic material, a baby cannot fully develop from a partial mole. Clusters of abnormal cells (called molar tissue) grow in the uterus (womb) instead. Sometimes a baby may be seen during an ultrasound scan. The baby will be smaller than expected, and it cannot survive to full term.

Even if you cannot see a baby on an ultrasound scan, the molar tissue will cause a positive pregnancy test. You'll also have pregnancy symptoms.

Often, a molar pregnancy causes no specific symptoms. Some people do have these:

• vaginal bleeding
• a dark discharge from the vagina that contains small, grape-like lumps
• severe morning sickness
• a high temperature
• an unusually swollen tummy
• high blood pressure
• protein in your pee, which might make your pee foamy, frothy or bubbly
• tiredness
• weakness
• twitching or trembling
• stomach pain

These symptoms can be normal in pregnancy, and having them doesn't mean there's definitely a problem with your baby. But you should still see a doctor, who can check you over.

Most molar pregnancies are picked up on a routine ultrasound scan, where the images look unusual. That alone isn't enough to be sure you have a molar pregnancy, so you'll be offered a blood test to confirm it.

Sometimes a molar pregnancy ends in an early miscarriage before anyone has diagnosed it. If that happens, you'd only learn it was a molar pregnancy if tests are done after the miscarriage.

A molar pregnancy happens because of a problem with the genetic information in an egg or sperm. Doctors don't know what causes that problem.

Some things can raise the risk of a molar pregnancy. You're more likely to have one if:

• you're a young person (under 18 years)
• you're over 45 years old
• you're of Asian origin
• you've had a molar pregnancy before
• you have a diet that is low in vitamin A

Even if you fit several of these, you most likely won't have a molar pregnancy. It's still a rare condition. Your chance is only a little higher than it is for people who don't fit into these groups.

A molar pregnancy cannot develop into a baby. There's no way to correct the amount of genetic material in the fertilised egg, so you'll need surgery to have the pregnancy removed.

Some people develop a gestational trophoblastic neoplasia (GTN) after a molar pregnancy. It's a rare form of cancer, but it is highly curable.

After your surgery, you'll be registered with the Hydatidiform mole follow-up centre, which is within Ninewells hospital in Dundee. The centre gives you follow-up appointments and watches for signs of GTN. They do this by checking the level of hCG (a pregnancy hormone) in your blood and urine (pee).

The centre will work with your local doctor to do the blood and urine tests, so you won't need to travel to Dundee to have them done.

You must not become pregnant again before you finish follow-up treatment. A new pregnancy makes your hCG levels rise, and then the specialists cannot tell if you've developed GTN.

Gestational trophoblastic neoplasia (GTN) is a very curable type of cancer. It can be caused by molar tissue growing in your uterus. Over 99% of people with GTN make a full recovery.

GTN is usually diagnosed when specialists find a high level of hCG in your blood or urine (pee). Unusual vaginal bleeding can also be a sign of it.

These specialists will talk through the treatment options with you. You may be offered:

• surgery to remove the tissue
• chemotherapy

If you have GTN, you should not become pregnant for a year after you finish chemotherapy. This is because, in rare cases, the GTN could come back.

Having had a molar pregnancy should not stop you from getting pregnant again.

If you've had one before, your chance of having another is higher than that of a person who has never had one. But the risk is still very small. Only 1 in 80 people who've had a molar pregnancy will have another.

A molar pregnancy can be very hard on you emotionally. You may grieve for the baby you lost, and feel frustrated because no one can tell you why it happened.

You may also feel anxious about GTN, especially while you wait for your follow-up treatment to finish.