Pregnancy is a time of great joy for an expectant mother, but it can also be a time of great anxiety. The two often go hand in hand, especially for a first time mum. 

If this is you, one way to allay your worries is to see your OB GYN regularly, preferably before you even try to conceive. Your doctor will map out your prenatal care plan, and monitor your health and the pregnancy as it develops. This is crucial because every stage of gestation carries its own risks to the mum and her baby. Some are preventable and treatable, while others have no known causes and  are beyond anyone’s control. One such example is a molar pregnancy.

Molar Pregnancy

To the pregnant women reading this, let us begin by saying that molar pregnancies are relatively rare. It happens in 1 out of every 1,000 pregnancies.1 Statistically speaking, an overwhelming majority of pregnancies are uncomplicated and result in healthy births.2 

So what is a molar pregnancy? A molar pregnancy, also referred to as hydatidiform mole, occurs as early as fertilisation. A defect in the trophoblasts or the cells that are supposed to develop into the placenta, causes it to develop into an abnormal mass or a tumor instead. These masses or tumors appear as water-filled sacs in grape-like clusters.3 

A molar pregnancy falls under a group of conditions called Gestational Trophoblastic Disease or GTD. Aside from molar pregnancies, GTD covers other diseases that involve rare tumors that form inside a woman’s uterus from the cells that would have otherwise developed into the placenta.4   

There are two types of molar pregnancies: complete and partial.

Complete Molar Pregnancy

A molar pregnancy is considered complete when no foetal tissue develops in the womb. This happens when the sperm ends up fertilising an empty egg. Therefore, only molar tissues develop. This is the more common type.

Partial Molar Pregnancy

In a partial molar pregnancy, an incomplete embryo and placenta may develop along with the molar tissues. This happens when a normal egg is fertilised by two (instead of the usual one) sperm, resulting in a non-viable embryo. Partial molar pregnancy is even rarer than complete molar pregnancy. 

Symptoms

  • Dark brown to bright red spotting or bleeding
  • Severe nausea and vomiting
  • Early preeclampsia
  • Pelvic pressure or pain
  • Rapid uterine growth
  • Vaginal passage of grape-like cysts

Most of these symptoms are not exclusive to molar pregnancy. In fact, they are quite similar to normal pregnancy symptoms or they can be symptoms of something else entirely. If you’re experiencing any of these symptoms, see an OB GYN for an accurate diagnosis.

Causes

Molar pregnancies are caused by the abnormal fertilisation of the egg resulting in an abnormal fetus. Instead of fetal tissue, the placental tissue forms a mass in the uterus instead.

This phenomenon can be narrowed down to chromosomal (genetic material) imbalance in the pregnancy. This happens when an egg, which doesn’t contain genetic information, fertilise with a sperm, or when a normal egg is fertilised by two sperm.

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Detection and Diagnosis

Most molar pregnancies are discovered only when a miscarriage occurs, but it can also be detected through a transvaginal ultrasound as early as eight to nine weeks of pregnancy.

A complete molar pregnancy may reveal:

  • The absence of an embryo
  • The absence of amniotic fluid
  • Thick molar tissues in the uterus

A partial molar pregnancy may reveal:

  • A growth-restricted embryo
  • Low amniotic fluid
  • Thick molar tissues in the uterus

Risk Factors

Although it is generally rare, certain factors increase the likelihood of developing a molar pregnancy. The women who are more at risk are typically:

  • Over 35 years old or under 20 years old
  • With a history of previous molar pregnancy
  • With a history of miscarriage
  • Of Asian ethnicity
    • Women from Southeast Asia and Korea have a slightly increased risk for a molar pregnancy. There have been some dietary theories proposed about why this may be the case.5

Treatment, Management, and Prevention

The typical treatment for molar pregnancies begin with removing the non-viable embryo and placenta from the uterus through vacuum suction (evacuation of uterus) procedure. The molar tissue will then be examined to confirm the molar pregnancy diagnosis. 

After an evacuation, for the next six months to a year, her hCG levels will be regularly checked through blood tests. Human Chorionic Gonadotropin or hCG is a hormone produced during pregnancy. If the hGC levels remain high after the evacuation procedure, it could mean than some molar tissue remains or has grown back in the uterus. 

This is the reason why women who go through molar pregnancy are advised to wait until after a year before trying to conceive again. It’s impossible to tell if the increased hCG levels in the blood is a result of a new pregnancy or because of the presence of molar tissue.

If molar tissue remains and continues to grow in the uterus after it has been surgically removed, it has developed into gestational trophoblastic neoplasia, a rare form of cancer. The risk of this developing is 15% in a complete mole and 0.5% in a partial mole. The doctor may recommend additional treatment, such as chemotherapy or medication. In very rare cases, this could progress to choriocarcinoma, a form of cancer that can spread to the other parts of the body. 

Whether you’re pregnant or not, planning to get pregnant or considering contraceptives, see your Gynaecologist regularly to properly monitor your reproductive health. Book a consultation with Dr. Pamela Tan today. 

Endnotes

1.  https://americanpregnancy.org/pregnancy-complications/molar-pregnancy/

2.  https://www.medicalnewstoday.com/articles/322634.php

3.  https://www.mayoclinic.org/diseases-conditions/molar-pregnancy/symptoms-causes/syc-20375175

4.  https://www.cancer.org/cancer/gestational-trophoblastic-disease/about/what-is-gtd.html

5.  https://obgyn.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1471-0528.2003.01413.x