Molar Pregnancy

Overview

A molar pregnancy is a rare complication where abnormal cells grow in the uterus instead of a healthy embryo. It happens when a fertilised egg has errors in its genetic material. The placenta grows into a mass of fluid-filled cysts and a baby cannot develop. It may still produce a positive pregnancy test because it makes the pregnancy hormone hCG. Most molar pregnancies are non-cancerous, but close follow-up is needed to make sure the abnormal tissue is completely gone.

It is rare. In the UK, about 1 in 600 to 1 in 1,000 pregnancies is a molar pregnancy. The number varies between regions and populations.

It can happen to anyone who becomes pregnant. The risk is higher in women under 20 or over 40, and in those who have had a molar pregnancy before.

Symptoms

Common symptoms

• Vaginal bleeding in early pregnancy, sometimes dark or watery
• Severe nausea and vomiting
• Pelvic pain or pressure
• A uterus that is larger than expected for the stage of pregnancy
• No fetal movement or heartbeat
• Passage of grape-like cysts from the vagina
• Anaemia or signs of an overactive thyroid, such as a fast heartbeat or feeling very warm

Symptoms in older adults

• Symptoms are the same as in younger women, but women over 40 have a higher risk of a molar pregnancy and may need closer monitoring.

Causes

Main causes

• A molar pregnancy is caused by genetic errors during fertilisation that lead to abnormal growth of cells.
• In a complete molar pregnancy, sperm chromosomes duplicate, but the egg's chromosomes are lost, so the placenta becomes a mass of cysts with no fetal tissue.
• In a partial molar pregnancy, the egg is fertilised by two sperm, resulting in extra chromosomes and some fetal tissue that does not develop normally.
• The abnormal tissue produces hCG, but it does not support a real pregnancy.

Risk factors

• Being under 20 or over 40 years old
• Having had a molar pregnancy before
• Having had previous miscarriages or infertility
• A diet low in carotene or folate (though this link is not fully proven)
• Certain ethnic backgrounds have higher rates, but the reasons are not fully understood.

When to see a doctor

See a doctor urgently if:

• If you have heavy vaginal bleeding, especially with clots or grape-like tissue.
• If you have severe pelvic or abdominal pain.
• If you have signs of infection, such as fever or chills.
• If you develop symptoms of pre-eclampsia, such as headache, changes in vision, or severe swelling.

Book a routine appointment if:

• If you experience any unusual vaginal bleeding during pregnancy.
• If you have severe nausea or vomiting that is unusual for you.
• If you had a molar pregnancy before and are planning to become pregnant again.

Diagnosis

A doctor will ask about your symptoms, do a pelvic examination, and order blood tests and an ultrasound scan. A molar pregnancy is often first identified on an ultrasound, which shows a distinctive 'cluster of grapes' pattern in the uterus.

Tests that may be done

• Blood test to measure hCG levels, which are often much higher than normal.
• An ultrasound scan of the uterus to look for abnormal tissue.
• Chest X-ray or CT scans to check if the abnormal tissue has spread, if there is concern.
• A tissue sample taken after surgery to confirm the diagnosis and decide the next steps.

What to expect at your appointment

You will be referred to an early pregnancy clinic or a gynaecologist. You will need a series of blood tests and scans. After treatment, you will be asked to avoid pregnancy for 6 to 12 months so that your hCG levels can be checked and any remaining tissue can be detected early.

Treatment

The goal of treatment is to remove the abnormal tissue and make sure it does not spread or return. The main treatment is surgery, and after that, you will need regular monitoring of hCG levels. If tissue remains, further treatment may be needed.

Self-care at home

• Follow your doctor's advice about rest and activity after surgery.
• Do not use tampons or have sexual intercourse until your doctor says it is safe, to reduce the risk of infection.
• Report any unusual bleeding, pain, or fever to your healthcare team.
• Eat a balanced diet and drink plenty of fluids to help your body recover.
• Give yourself time to recover emotionally. This is a pregnancy loss, and you may need support.

Medical treatments

After surgery, your hCG levels will be checked regularly. If the levels do not fall to normal, or if abnormal tissue has spread, you may need additional treatment. This is usually chemotherapy, which is a type of medicine given by mouth or through a drip that targets and destroys the abnormal cells. The exact treatment plan depends on the type of molar pregnancy, the hCG levels, and whether the tissue has spread. Your specialist team will explain the options and what to expect.

When is surgery considered?

The most common first treatment is a surgical procedure to empty the uterus, called suction curettage. It is usually done under general anaesthesia. In rare cases, if you have completed your family and there is a high risk of the tissue spreading, a hysterectomy may be recommended. That is the surgical removal of the whole uterus.

Living with this condition

After treatment, you will have regular check-ups and blood tests for at least 6 months, and often longer. It is important not to become pregnant during this time, so you will need to use reliable contraception every time you have sex. Once your hCG levels have been normal for 6 months, your doctor may give you the all-clear to try for another pregnancy.

Lifestyle tips

• Use contraception as advised by your doctor until your hCG levels are normal.
• Attend every follow-up appointment and blood test.
• Avoid alcohol and tobacco to help your body recover.
• Let yourself rest in the days after surgery and gradually build up activity.

Diet and exercise

There is no special diet for a molar pregnancy, but eating a varied diet with plenty of vegetables, fruits, and protein helps your body recover. Gentle exercise, such as walking, is safe once you feel able. Avoid hard or intense exercise until your doctor has cleared you.

Mental health and emotional wellbeing

A molar pregnancy is a deeply emotional experience. It is a pregnancy loss, and the months of monitoring can bring stress and uncertainty. You may feel grief, guilt, anger, or fear. These are normal feelings. Speaking with a counsellor or joining a support group can help, and you do not have to go through this alone.

Prevention

There is no known way to prevent a molar pregnancy because it happens due to random genetic errors. If you have had one, you are at higher risk of another, so your doctor will want to monitor any future pregnancy carefully. Good preconception health may support a healthy pregnancy in general, but it cannot guarantee prevention.

Screening programmes

If you have had a molar pregnancy before, your doctor may recommend an early ultrasound scan and blood hCG test in any future pregnancy. This is a precaution to confirm the pregnancy is developing normally and to identify any possible problems early.

Complications

If left untreated

• Heavy vaginal bleeding that can be life-threatening.
• The abnormal tissue can grow into the muscle layer of the uterus.
• The tissue can spread outside the uterus to other parts of the body, which is called gestational trophoblastic neoplasia.
• Persistent high hCG levels may require chemotherapy.
• Damage to the uterus that could affect future pregnancies.

Long-term outlook

With proper treatment and follow-up, most people with a molar pregnancy recover fully. Around 8 out of 10 complete moles are cured by the first surgical removal alone, and for those who need more treatment, the cure rate is very high. After monitoring is complete, most women can go on to have healthy pregnancies. The journey can be hard, but there is strong hope and your healthcare team will support you at every step.

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