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What Is A Twin Molar Pregnancy?

Twin molar pregnancy is a rare form of pregnancy in which a viable fetus coexists with a mole. A mole is a group of abnormal cells that are formed when genetic material of sperm and ovum are not transferred properly during fertilization. It usually contains genetic material from the father and misses the genetic material from the mother. Twin molar pregnancy possesses the risk of developing gestational trophoblastic neoplasia in the mother. It may also engulf the viable fetus too. Therefore, it is recommended to terminate the pregnancy to avoid the risk of cancer.

What Is A Twin Molar Pregnancy?

What Is A Twin Molar Pregnancy?

Twin molar pregnancy is characterized by the development of a viable baby and a mole together in two different sacs in the same pregnancy. The viable fetus grows as the stages of pregnancy and may have normal heartbeat also. But it can be influenced by the speedy growth of the mole. The mole may influence the nourishment of the viable baby. The mole becomes so large that it may engulf the viable baby also. The viable baby may also have the chances of having chromosomal abnormalities as the reasons stated above. The viable baby even if survives in pregnancy, may not survive long after birth. In rare cases, the baby can survive.

Twin molar pregnancy also has the risk of developing cancer in the mother. The abnormal sets of cells are present in the womb that may continue to grow during the later stages of the pregnancy. They may extend deep inside the uterus. This condition is known as gestational trophoblastic neoplasia (GTN). It may also travel to different parts of the body like the lungs, heart and other organs. This condition is known as persistent trophoblastic disease. This disease leads to extreme damage to the uterus that may decrease the chances of next pregnancy and may cause uterine diseases. It also results in the development of cancer in the mother.

The better way to prevent these complications is to terminate the pregnancy. In severe cases of GTN, hysterectomy i.e. surgical removal of the uterus is performed.

Molar pregnancy is a rare complication of pregnancy that is marked by the growth of an abnormal group of cells called mole. This condition is also known as hydatidiform mole. It develops in the placenta during pregnancy instead of a fetus. The growth of this mole is faster than a normal fetus. It resembles a large bunch of grapes and forms clusters of the cells.

Causes Of Molar Pregnancy

It is formed when a certain amount of genetic information are not coded in the fertilized egg. Or the exchange of genes and chromosomes is not proper between the sperm and ova during fertilization. It is formed due to deletion or inactivity of chromosomes of the mother and addition of all chromosomes of the father.

Risk Factors For Molar Pregnancy

  • Age – women who are above the age of 40 years and below 20 years has more chances of having a molar pregnancy.
  • Race – there are higher chances of one or more molar pregnancies in races that belong to Southeast Asia, Philippines and Mexico. White women have higher chances of molar pregnancy than black women.
  • Medical History– women who have the previous history of molar pregnancy can have another molar pregnancy. The women who have a history of miscarriages can develop molar pregnancy. In recent studies, it is revealed that reproductive techniques like IVF done for infertile couples can induce molar pregnancy.


Twin molar pregnancy is a rare complication of pregnancy featured with a viable fetus and a hydatidiform mole. In this pregnancy, the viable fetus may grow into a normal baby but the mole grows at a faster pace than the fetus. The mole may influence the growth of the fetus and may eat the fetus. It may also risk the mother of developing cancer if not removed.


  1. The American College of Obstetricians and Gynecologists (ACOG): https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2018/07/gestational-trophoblastic-disease
  2. NHS (National Health Service): https://www.nhs.uk/conditions/molar-pregnancy/
  3. The Lancet: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00636-3/fulltext
  4. Indian Journal of Cancer: https://www.indianjcancer.com/article.asp?issn=0019-509X;year=2019;volume=56;issue=4;spage=317;epage=321;aulast=Malik
  5. MedlinePlus: https://medlineplus.gov/ency/article/001498.htm

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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 4, 2023

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