What causes a molar pregnancy?

Molar pregnancy is usually caused by a faulty or abnormal fertilization process. Although some studies have linked molar pregnancy with dietary or genetic factors, the real cause of molar pregnancy is still unknown.
Molar pregnancy is usually caused by a faulty or abnormal fertilization process. Although some studies have linked molar pregnancy with dietary or genetic factors, the real cause of molar pregnancy is still unknown.

The exact cause of molar pregnancy is still being researched. However, it should be agreed that molar pregnancy is usually caused by a faulty or abnormal fertilization process. In a normal conception, each parent contributes 23 chromosomes to make 46 chromosomes in total. Molar pregnancy is of two types

  1. Complete molar pregnancy
  • The number of chromosomes (46) is normal, but they all come from the father. A complete molar pregnancy occurs when an empty egg (no chromosomes) is fertilized by two sperm.
  • Thus, two paternal sets of chromosomes are seen in a complete mole.
  • In a complete molar pregnancy, a sperm fertilizes an empty egg, so the only genetic material inside comes from the father.
  • This forms a mass of abnormal placenta-like cells but no developing baby.

       2. Partial molar pregnancy

  • Two sperm fertilize a single egg and then there are 69 chromosomes.
  • Partial mole occurs when a normal egg follicle is fertilized by two sperm, thus leading to three sets of chromosomes (triploidy).
  • In a partial molar pregnancy, there’s too much genetic material inside.
  • The baby may start to develop but doesn’t develop properly.
  • It is genetically abnormal and unable to live beyond three months.

Although some studies have linked molar pregnancy with dietary or genetic factors, the real cause of molar pregnancy is still unknown. A molar pregnancy happens when there are certain problems with the genetic code (the chromosomes) in the fertilized egg. The result is that the egg may develop into growth with no embryo (this is called a complete mole) or an abnormal embryo (a partial mole). The possible causes and risk factors of molar pregnancy may include

  • Women who are older than 35 or younger than 20 years old. Compared to women who are between 20 to 40 years old, the risk for pregnant girls younger than 15 years old is approximately 1.5 times higher and for women who are 45 years old or older, the risk is 20 to 50 times higher.
  • Asian ethnicity.
  • Previous history of molar pregnancy. A repeat molar pregnancy happens (an average of 1 out of every 100 women).
  • Women with possible ovulatory disorders.
  • Women with a history of miscarriage.
  • A diet low in folic acid or carotene. Carotene is a form of vitamin A. Women who don't get enough of these vitamins have a higher rate of complete molar pregnancy.

What are the signs and symptoms of molar pregnancy?

A molar pregnancy happens when tissue that is supposed to become a fetus becomes an abnormal growth or tumor inside the uterus. Even though it isn't an embryo, this growth triggers symptoms of pregnancy. Most of the signs and symptoms correlate with normal pregnancy. Even though you might have typical pregnancy symptoms, the following may happen

  • The patient may have some spotting or heavier bleeding. It might be continuous or intermittent, light or heavy bright and red or a brownish discharge.
  • This bleeding could start as early as six weeks into the molar pregnancy or as late as 12 weeks.
  • Passing grape-like material via the vagina.
  • High blood pressure.
  • The uterus looks too big for the corresponding pregnancy duration.
  • The patient might also have severe nausea and vomiting, abdominal cramping and abdominal swelling (because your uterus may grow more rapidly than usual).

The doctor may perform an abdominal ultrasound and may also do a blood test to measure your pregnancy hormone levels.

  • The ultrasound will show cysts that look like a cluster of grapes in the uterus.
  • Pregnancy hormone levels will be higher than normal.

How is a molar pregnancy treated?

There are two ways to treat a molar pregnancy. Your doctor will discuss them with you and may recommend one over the other. These options include

Surgical management

  • This is the preferred choice of treatment in most molar pregnancies
  • If the doctor suspects that you have a complete molar pregnancy, you will be offered surgery. This is usually done under general anesthesia.
  • The tissue is removed from your uterus and sent to the pathology laboratory to check the diagnosis.

Medical management

  • This is an alternative option if a complete molar pregnancy is not suspected. However, it can be more difficult to obtain sufficient tissue for the laboratory to make a definite diagnosis.
  • Medication is given to cause the molar pregnancy to miscarry. You may need to stay in the hospital until you have passed the pregnancy tissue. The pregnancy tissue is then collected and sent to the pathology laboratory to check the diagnosis.

Gestational trophoblastic disease (GTD)

  • After a molar pregnancy has been removed, some molar tissue may persist and continue to grow. It occurs usually after a complete mole treatment rather than a partial mole.
  • The absolute sign of the disease is persistently high levels of human chorionic gonadotropin (HCG) even after the molar pregnancy is treated.
  • In some cases, an invasive mole penetrates deep into the middle layer of the uterine wall, which causes vaginal bleeding.
  • Persistent GTD can nearly always be successfully treated, most often with chemotherapy.
  • Another treatment option is the removal of the uterus (hysterectomy).
  • Rarely, a cancerous form of GTD known as choriocarcinoma develops and spreads to other organs. Choriocarcinoma is usually successfully treated with multiple cancer drugs.

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Medically Reviewed on 2/19/2021
References
Medscape Medical Reference