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Are Molar Pregnancies Hereditary?

Molar pregnancy is caused due to the fertilization of sperms with abnormal egg. The egg does not contain the DNA material resulting in unviable pregnancy. Formation of hydatidiform mole is the characteristic feature and may also involve hereditary angle.

Are Molar Pregnancies Hereditary?

Are Molar Pregnancies Hereditary?

Recurrent hydatidiform mole is affected by the genetic mutation. The genes involved are NLRP7 and KHDC3L, which are responsible for the development of oocyte. Mutation in these, results in abnormal development. The condition is inherited in an autosomal recessive pattern.

Molar pregnancy is characterized by the preset of hydatidiform mole. This is formed due to abnormal development of a mass of tissue which indicates like a fetus in the initial stages. There is two type of molar pregnancy, the complete molar pregnancy in which the sperm fertilizes with an egg which does not have any DNA. The other is partial molar pregnancy which is developed when two sperms fertilize with one egg. Both the cases result in the unviable fetus and an increase in the level of hCG hormone. When the molar pregnancy occurs at least two times, the condition is termed as a recurrent hydatidiform mole (RHM). According to the research, a genetic angle is associated with the occurrence of recurrent hydatidiform mole. The condition is due to the mutation in various genes, however, two important genes, the mutation of which causes a maximum number of the recurrent hydatidiform mole are NLRP7 and KHDC3L.

There are two processes related to oocyte or egg cell. One is the formation of oocyte while other is the development of the formed oocyte. Research has indicated that a maximum number of recurrent hydatidiform moles occur due to the mutation of genes which are responsible for oocyte development while fewer cases of the recurrent hydatidiform mole are seen in patients with faulty genes responsible for oocyte production.

NLRP7 and KHDC3L are the genes responsible for the development of oocyte and any mutation in these genes results in abnormal development of egg cells. Pregnancy resulting from the fertilization of such oocyte is not viable and hence results in the formation of hydatidiform mole. As the genetic disorder is associated with the development of oocyte, this condition leads to the recurrent hydatidiform mole.

Mutation in these genes results in the prevention of DNA exchange and the oocyte so formed is devoid of any genetic material. These genes are responsible for the production of a normal egg cell.

The condition is an autosomal recessive condition which means that to present the effect; both the copies of genes should be mutated. If there is a single copy of the mutated gene, the other non-mutated gene will function normally and thus no symptoms of gene mutation would be presented.

The rate of occurrence of hydatidiform mole is 1 in 600 to 1 in 1000 pregnancies. The rate of recurrent hydatidiform mole is 1 to six percent of the women with previous hydatidiform mole. The unviable pregnancy is to be removed with surgery and there are chances that the remaining tissue may lead to a malignant condition such as gestational choriocarcinoma. However, this condition is rare and has the incidence rate of 1 in 20000 to 1 in 50000 pregnancy cases.

Symptoms of Molar Pregnancy

Following are the symptoms associated with molar pregnancy:

Vaginal Bleeding. The patients experience increased vaginal bleeding due to molar pregnancy.

Ultrasound Characteristics. Molar pregnancy shows distinct characteristics in the uterus. The chronic villi are enlarged and there is an increasing proliferation of trophoblast cells. Further, the mom is formed like a bunch of grapes and presents a pattern of a snowstorm. Trophoblast also has impaired angiogenesis.

Nausea And Vomiting. Patient may also experience nausea and vomiting due to an altered level of hormones.

Preeclampsia. The blood pressure of the patients may also increase and also shows the presence of proteins in the urine.

Anemia. Due to severe bleeding, the patient may suffer from anemia. Also, there is an abnormally increased level of hCG hormone.

Disproportionate Uterine Growth. Uterine growth is disproportionate with time i.e. the uterine growth is high as compared to the stage of pregnancy.


  1. The New England Journal of Medicine: Genetic Mutations in Recurrent Hydatidiform Moles – https://www.nejm.org/doi/full/10.1056/NEJMoa0707346
  2. National Organization for Rare Disorders (NORD): Hydatidiform Mole – https://rarediseases.org/rare-diseases/hydatidiform-mole/
  3. Genetics Home Reference: NLRP7 Gene – https://ghr.nlm.nih.gov/gene/NLRP7
  4. Genetics Home Reference: KHDC3L Gene – https://ghr.nlm.nih.gov/gene/KHDC3L
  5. Journal of Reproductive Medicine: Recurrent Hydatidiform Moles: A Puzzle Worth Solving – https://pubmed.ncbi.nlm.nih.gov/2530259/
  6. Journal of Ultrasound in Medicine: Ultrasound Diagnosis of Early Complete Hydatidiform Mole – https://pubmed.ncbi.nlm.nih.gov/22104063/
  7. American Journal of Obstetrics and Gynecology: Management and prognosis of complete hydatidiform mole – https://pubmed.ncbi.nlm.nih.gov/21890084/
  8. Cancer Treatment Reviews: Gestational choriocarcinoma: An unusual case of suspected appendicitis – https://pubmed.ncbi.nlm.nih.gov/30577932/

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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:July 20, 2023

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