Molar pregnancy is a rare pregnancy complication in which an egg gets fertilised by a sperm incorrectly, leading to the formation of non-cancerous cysts instead of a placenta. In the absence of a healthy placenta, an embryo fails to develop normally and may lead to pregnancy loss.

What is molar pregnancy?

Molar pregnancy, also called hydatidiform mole, is a rare complication where a tumour is formed in the uterus which causes the placenta to become a mass of cysts, an abnormal pocket of fluid. A molar pregnancy is not known to last because the placenta cannot nourish the foetus, explains obstetrician and gynaecologist Dr Bharathi Ramesh. The incidence rates of molar pregnancy varies among different parts of the world, still it is rare. It ranges between 0.2 to 9.9 per 1, 000 pregnancies, as per a a research published in the Placenta journal in 2021.

While it can happen to any woman, associated risk factors include advanced age of the mother that is 35 years and above, and a history of previous abortions, as per a 2018 research published in the Obstetrics and Gynecology International journal.

This kind of pregnancy is a type of gestational trophoblastic disease or GTD, which is a group of conditions causing tumours to grow in your uterus.

Types of molar pregnancy

There are mainly two types of molar pregnancy:

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1. Complete molar pregnancy

In this type, no embryo gets formed. It occurs when a sperm fertilises an empty egg, and as the egg is empty, the embryo is unable to grow.

2. Partial molar pregnancy

It happens when an abnormal placenta gets formed along with an embryo. Two sperm fertilise one egg, the embryo may begin to develop, but generally is unable to survive.

What are the symptoms of molar pregnancy?

A molar pregnancy may feel like a normal pregnancy at first, but look for these signs:

• Vaginal bleeding that might have tissue clots
• Unusually high pregnancy hormone levels or HCG levels
• Nausea and vomiting
• Pelvic pain
• Anemia
• High blood pressure of preeclampsia

What are the causes of molar pregnancy?

A molar pregnancy is usually caused by abnormalities in the chromosomes that can come in the way of the embryo’s development, and lead to the growth of a tumour, says the expert. For instance, sometimes the maternal chromosomes may be missing while the paternal chromosomes may be duplicated. In some cases, an egg is fertilised by two sperms which results in three sets of chromosomes. In other cases, a molar pregnancy is a result of an imperfect egg or sperm getting fertilised.

Can a woman have a healthy baby with molar pregnancy?

Unfortunately, a molar pregnancy cannot result in the birth of a healthy baby. This is because a normal foetus does not develop in the uterus, and even in rare cases it does, it is usually not viable and cannot grow into a healthy baby, says Dr Bharathi. Also, in a molar pregnancy, since the placenta becomes an abnormal sac of fluids, it cannot nourish and support the development of the foetus.

How is molar pregnancy diagnosed?

When you go for a check-up, you may find out about this rare pregnancy complication during your the first ultrasound scan when you are around 8 to 14 weeks pregnant, according to the UK’s National Health Service.

If you show symptoms of a molar pregnancy, your doctor can diagnose it with a transvaginal ultrasound. To determine the type of mole, further testing like X-ray, CT scans or MRI, may be needed.

What are the treatment options for molar pregnancy?

Some molar pregnancies are treated in spontaneous abortion or miscarriage. But it is important to make sure that the entire growth is removed, and so, a surgery is the preferred treatment for a molar pregnancy. Also, depending on the type of mole and how far it has spread, different treatment methods like chemotherapy, radiation and hysterectomy can be used. After the mole has been removed, you will be monitored for six or more months.

Can a woman get pregnant again after having a molar pregnancy?

Yes, you can have a completely normal and successful pregnancy after experiencing a molar pregnancy. But it is advised to wait for some time, at least six months to a year, before trying to conceive again, says the expert. During this time, regular follow-up appointments and monitoring are important to ensure that the molar pregnancy has been successfully treated and that there are no signs of it happening again.

A molar pregnancy is relatively rare but once you have had one, the chances of having another one in subsequent pregnancies are slightly more. This can be due to several factors such as age and a history of miscarriages.

As for prevention, there are not many known ways to prevent a molar pregnancy. But early prenatal care, a healthy lifestyle, genetic counselling, and regular check-ups might reduce the risk or help in early detection.