Molar Pregnancy

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Molar pregnancy is an abnormal pregnancy in which the chorionic villi surrounding the ovum is converted into a mass of cysts or vesicles of varying sizes.

Molar pregnancy is also called Gestational Trophoblastic Disease and the abnormally developing ovum is called the vesicular Mole or the Hydatidiform Mole. The name comes from the similarity to the hydatid cysts formed in infections by liverflukes.

A Molar pregnancy results from over-production of the tissue that is supposed to develop into the placenta.

Cause of Molar Pregnancy

The cause of the occurance of molar pregnancy is still under research, but it is believed to be paternal in origin. The mole shows two X-chromosomes which have been identified as coming from the male partner. It is thought that fertilization of an ovum by a sperm carrying two X-chromosomes or by two sperms carrying an X-chromosome each, causes the development of a vesicular mole (normal sperms carry either a X- or a Y-chromosome).

Molar pregnancy usually starts developing from the 8th week of pregnancy, although it has been identified as early as the 3rd week.

Types of Molar Pregnancy

  • Partial Mole: There is some amount of normal placental tissue and a fetus together with abnormal molar tissue.

  • Complete Mole: There is no normal placental tissue or fetus. The entire pregnancy sac is converted into vesicles.

    Partial Hydatidiform Mole

    Complete Hydatidiform Mole

    Signs and Symptoms of Molar Pregnancy

    • Age: It is more common in pregnancies after the age of 40 years.

    • Signs and symptoms: All the signs and symptoms of early pregnancy are present.

    • Morning Sickness: Morning Sickness in early pregnancy is usually severe (So a patient who complains of severe vomiting should always be checked for Hydatidiform Mole).

    • Size of the uterus: The uterus is usually larger than the normal size for the month of pregnancy by date.

    • Vaginal Discharge: Recurrent bloodstained vaginal discharge or passage of frank blood is the commonest symptom. Occasionally there may even be passage of vesicles through the vagina.

    • Pain: There is no pain in the abdomen unless the mole is in the process of spontaneous expulsion.

    • Anemia: Anemia can occur due to bleeding or rarely due to folate deficiency caused by the rapidly developing vesicles.

    • Thyrotoxicosis:Thyrotoxicosis, which is a disease with an increase in circulating thyroid hormones, can occur but is relatively uncommon. If it does, then there may be symptoms like heat intolerance, palpitation, restlessness, etc.

    • Symptoms of Pre-eclampsia Pre-eclampsia or PET which occurs in the 1st trimester or early 2nd trimester is usually due to molar pregnancy.

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    Tests for Molar Pregnancy

    • Ultrasound - Molar pregnancy is easily identified in an ultrasound - the vesicles show up in a typical appearance known as the 'snowstorm' appearance.

    • Human Chorionic Gonadotrophin (HCG) The levels of the HCG hormone level is very high. This high level shows up in both blood and urine. For example, HCG level in urine at 12-16 weeks of normal pregnancy varies in the range 10,000-30,000 I.U. per liter. In molar pregnancy, the level may go as high as 350,000-3,000,000 I.U. per liter.

    • Blood Tests: A complete blood count, blood clotting tests and tests for thyroid hormone levels are needed.

    Complications of Molar Pregnancy

    The most feared complication of Hydatidiform Mole is Choriocarcinoma. This is a malignant form of the disease which can occur simultaneously with the development of the mole, or later, after 6 months of evacuation of the Mole.
    Other complications are hemorrhage, sepsis or perforation of the uterus.

    Treatment of Molar Pregnancy

    The broad guidelines of treatment are:

    • Early evacuation of the mole: The mole is removed from the uterus slowly and gently, taking care not to injure the walls of the uterus as they tend to be very friable in this disease.

    • Follow-up of Molar Pregnancy: The patient has to be followed up for at least two years after evacuation for early detection of malignant changes.

      Serum HCG levels are measured every 2 weeks until it reaches normal levels (usually in about 4 weeks time after delivery), then monthly for 6 months, then 2 monthly for another 6 months, then 6 monthly for the next 1 year. This makes up a total follow-up time of 2 years.

      The patient is not allowed to get pregnant within this time. She should use barrier contraceptives like condoms. Hormone containing contraceptives like birth control pills should be taken.

    • Rising HCG titre: If serum HCG levels show rising titre, the patient needs to be investigated for the development of choriocarcinoma.

    • Hysterectomy: If the patient has completed her family and HCG is detected in the urine even after 6 months, hysterectomy (removal of the uterus) may be advised, as these women are likely to develop choriocarcinoma.

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