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A.D.A.M. Medical Encyclopedia [Internet]. Atlanta (GA): A.D.A.M.; 2013.

A.D.A.M. Medical Encyclopedia.

Hydatidiform mole

Hydatid mole; Molar pregnancy

Last reviewed: November 8, 2012.

Hydatidiform mole is a rare mass or growth that forms inside the womb (uterus) at the beginning of a pregnancy. It is a type of gestational trophoblastic disease (GTD). A cancerous form of GTD is called choriocarcinoma.

Causes

Hydatidiform mole, or molar pregnancy, results from over-production of the tissue that is supposed to develop into the placenta. The placenta feeds the fetus during pregnancy. With a molar pregnancy, the tissues develop into an abnormal growth, called a mass.

There are two types:

  • Partial molar pregnancy: There is an abnormal placenta and some fetal development.
  • Complete molar pregnancy: There is an abnormal placenta but no fetus.

Both forms are due to problems during fertilization. The exact cause of fertilization problems is unknown. A diet low in protein, animal fat, and vitamin A may play a role.

Symptoms

Exams and Tests

A pelvic examination may show signs similar to a normal pregnancy, but the size of the womb may be abnormal and the baby's heart sounds are absent. There may be some vaginal bleeding.

A pregnancy ultrasound will show an abnormal placenta with or without some development of a baby.

Tests may include:

Treatment

If your doctor suspects a molar pregnancy, a suction curettage (D and C) may be performed.

A hysterectomy may be an option for older women who do not wish to become pregnant in the future.

After treatment, serum HCG level will be followed. It is important to avoid pregnancy and to use a reliable contraceptive for 6 - 12 months after treatment for a molar pregnancy. This allows for accurate testing to be sure that the abnormal tissue does not grow back. Women who get pregnant too soon after a molar pregnancy have a high risk of having another molar pregnancy.

Outlook (Prognosis)

More than 80% of hydatidiform moles are benign (noncancerous). Treatment is usually successful. Close follow-up by your doctor is important. After treatment, use effective contraception for at least 6 - 12 months to avoid pregnancy.

In some cases, hydatidiform moles develop into invasive moles. These can grow deep into the uterine wall and cause bleeding or other complications.

In a few cases, a hydatidiform mole develops into a choriocarcinoma. This is a fast-growing cancerous form of gestational trophoblastic disease. 

Possible Complications

Lung problems may occur after a D and C if the mother's uterus is larger than 16 weeks gestational size.

Complications of molar pregnancy include:

Complications related to the surgery to remove a molar pregnancy include:

  • Excessive bleeding
  • Side effects of anesthesia

References

  1. Copeland LJ, Landon MB. Malignant diseases and pregnancy. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics - Normal and Problem Pregnancies. 6th ed. Philadelphia, Pa: Elsevier Saunders; 2012:chap 47.
  2. Goldstein DP, Berkowitz RS. Gestational trophoblastic disease. In: Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, McKenna WG, eds. Abeloff’s Clinical Oncology. 4th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 94.
  3. Kavanagh JJ, Gershenson DM. Gestational trophoblastic disease: hydatidiform mole, nonmetastatic and metastatic gestational trophoblastic tumor: diagnosis and management. In: Katz VL, Lentz GM, Lobo RA, Gershenson DM, eds. Comprehensive Gynecology. 6th ed. Philadelphia, Pa: Elsevier Mosby; 2012:chap 35.

Review Date: 11/8/2012.

Reviewed by: Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.

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The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

What works?

  • Prophylactic (preventive) chemotherapy for hydatidiform mole (molar pregnancy) to prevent cancerous growth laterProphylactic (preventive) chemotherapy for hydatidiform mole (molar pregnancy) to prevent cancerous growth later
    A molar pregnancy (hydatidiform mole) develops following an abnormal process of conception, whereby placental tissue overgrows inside the womb (uterus). Molar pregnancies are classified as complete (CM) or partial (PM) based on their appearance (gross and microscopic), and their chromosome pattern. Moles are usually suspected at the early pregnancy scan and women often present with bleeding, similar to a miscarriage. The molar tissue is removed by evacuation of retained products of conception (ERPC), also known as dilatation and curettage (D&C) and women generally make a full recovery. However, some women go on to develop a cancer in the womb (about 1 in every 5 women with a CM and 1 in 200 with a PM). Women are generally at a higher risk of getting this cancer, which is known as gestational trophoblastic neoplasia (GTN), if they are over 40 years old, have a large increase in the size of the womb, have large cysts in the ovaries or have high initial levels of β‐human chorionic gonadotrophin (hCG) (the pregnancy hormone) in their blood. Although treatment of the cancer with chemotherapy (anti‐cancer drugs) is almost always effective, it has been suggested that routinely giving women anti‐cancer drugs (P‐Chem) before or after the removal the molar tissue may reduce the risk of the cancerous tissue developing.
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Figures

  • Uterus.
    Normal uterine anatomy (cut section).

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