| Molar pregnancy | |
|---|---|
| Other names | Hydatid mole, hydatidiform mole |
_complete_type.jpg) | |
| Histopathologic image of hydatidiform mole (complete type). H&E stain. | |
| Specialty | Obstetrics |
A molar pregnancy, also known as a hydatidiform mole, is an abnormal form of pregnancy in which a non-viable fertilized egg implants in the uterus. It falls under the category of gestational trophoblastic diseases.[1] During a molar pregnancy, the uterus contains a growing mass characterized by swollen chorionic villi, resembling clusters of grapes.[2] The occurrence of a molar pregnancy can be attributed to the fertilized egg lacking an original maternal nucleus. As a result, the products of conception may or may not contain fetal tissue. These molar pregnancies are categorized into two types: partial moles and complete moles, where the term 'mole' simply denotes a clump of growing tissue or a ‘growth'.
A complete mole is caused by either a single sperm (90% of the time) or two sperm (10% of the time) combining with an egg that has lost its DNA. In the former case, the sperm reduplicates, leading to the formation of a "complete" 46-chromosome set.[3] Typically, the genotype is 46,XX (diploid) due to subsequent mitosis of the fertilizing sperm, but it can also be 46,XY (diploid).[3] However, 46,YY (diploid) is not observed. On the other hand, a partial mole occurs when a normal egg is fertilized by one or two sperm, which then reduplicates itself, resulting in genotypes of 69,XXY (triploid) or 92,XXXY (tetraploid).[3]
Complete moles carry a 2–4% risk, in Western countries, of developing into choriocarcinoma and a higher risk of 10–15% in Eastern countries, with an additional 15% risk of becoming an invasive mole. In contrast, incomplete moles can become invasive as well but are not associated with choriocarcinoma.[3] Notably, complete hydatidiform moles account for 50% of all cases of choriocarcinoma.
Molar pregnancies are relatively rare complications of pregnancy, occurring in approximately 1 in 1,000 pregnancies in the United States, while in Asia, the rates are considerably higher, reaching up to 1 in 100 pregnancies in countries like Indonesia.[4]
- ^ "About molar pregnancy | Gestational trophoblastic disease (GTD) | Cancer Research UK". www.cancerresearchuk.org. Retrieved 18 June 2022.
- ^ "hydatidiform mole". Merriam Webster. Retrieved May 7, 2012.
- ^ a b c d Kumar V, ed. (2010). Pathologic Basis of Disease (8th ed.). Saunders Elsevier. pp. 1057–1058. ISBN 978-1-4377-0792-2.
- ^ Di Cintio E, Parazzini F, Rosa C, Chatenoud L, Benzi G (November 1997). "The epidemiology of gestational trophoblastic disease". General & Diagnostic Pathology. 143 (2–3): 103–8. PMID 9443567.