What Causes Molar Pregnancy?

The causes of molar pregnancy are not known, indicating it occurs by chance, and women have no control over any of the factors that lead to it. Molar pregnancies can happen to women of all ages, ethnicities, and backgrounds.

In a molar pregnancy, an egg and sperm incorrectly join during fertilisation, resulting in a noncancerous tumour. Resembling small water-filled sacs that appear similar to a bunch of grapes, the tumour lacks the capacity to sustain embryo development, resulting in the loss of pregnancy. Some women end up having a miscarriage, while others need medical intervention to remove the tumours. If left untreated, molar pregnancies can lead to serious complications.


Complete vs. Partial Molar Pregnancy

Molar pregnancies can be categorised into two types: complete and partial molar pregnancies.

Complete molar pregnancy: In the case of a complete molar pregnancy, there is no development of the embryo. This happens when a sperm fertilises an egg that lacks the complete genetic information required for embryo growth. However, the placental tissue continues to grow but in an abnormal way, consisting of fluid-filled sacs (tumours). This placental tissue also produces the HCG hormone-like normal placental tissue does during a healthy pregnancy and gives positive results on pregnancy tests.

Partial Molar Pregnancy: In this condition, two sperm cells fertilise the same egg, leading to the embryo having 69 chromosomes instead of 46. An abnormal placenta also forms along with the embryo. Although the embryo continues to grow, it usually does not survive.

What Are the Symptoms of Molar Pregnancies?

Some women may not experience any symptoms of molar pregnancy. The ones who do experience the following:

  • Vaginal bleeding within the first three months of pregnancy
  • Severe nausea and vomiting
  • Cysts in a grape-like shape being discharged from the vagina.
  • Extremely high blood pressure (preeclampsia)
  • Abnormally elevated HCG levels
  • Abdominal swelling
  • No foetal movement or heartbeat

What Are the Risk Factors for Molar Pregnancies?

While the condition is rare (1 out of 1000 pregnancies) and can happen to any woman, there are certain risk factors that can be the causes of molar pregnancy, such as:

  • A previous molar pregnancy
  • Pregnant women younger than 20 or older than 40
  • Have had two or more miscarriages.
  • The woman is of South Asian descent.

How Is Molar Pregnancy Treated?

The embryo in a molar pregnancy will not grow into a healthy foetus; hence, it is essential to receive appropriate treatment to avoid complications. The molar pregnancy treatment typically involves:

  1. Dilation and Curettage (D&C)During the D&C procedure, the cervix (opening to the womb) is dilated, and the harmful tissue inside is sucked out using a medical vacuum. The procedure is performed under general anaesthesia or through local numbing.
  2. Chemotherapy drugsIn high-risk molar pregnancies, where the chances of cancer are substantial, doctors would recommend chemotherapy. The treatment is given after D&C if the HCG levels continue to stay elevated over time.
  3. RhoGAMWomen who have the Rh-negative blood type would be given a drug called RhoGAM along with the rest of the treatment. The purpose is to prevent these complications from developing antibodies. Women who have a negative blood type, such as A-, B-, O- or AB-, are given RhoGAM.
  4. HysterectomyThe hysterectomy is a major surgery to remove the uterus. It is not a common treatment for molar pregnancies and is only performed under specific circumstances. It is performed when the woman no longer wishes to get pregnant.


Molar pregnancies are rare but can happen to all women. It is important to stay vigilant, especially if the woman has experienced a molar pregnancy before and look for the symptoms of molar pregnancy. The long-term prognosis is positive for most women, and they can go on to have healthy pregnancies in the future.