Molar pregnancy

Source: Wikipedia, the free encyclopedia.
Molar pregnancy
Other namesHydatid mole, hydatidiform mole
Histopathologic image of hydatidiform mole (complete type). H&E stain.
SpecialtyObstetrics

A molar pregnancy, also known as a hydatidiform mole, is an abnormal form of

mole
' simply denotes a clump of growing tissue or a ‘growth'.

A complete mole is caused by either a single

tetraploid).[3]

Complete moles carry a 2–4% risk, in Western countries, of developing into

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]

Signs and symptoms

Vesicular mole

Molar pregnancies usually present with painless vaginal bleeding in the fourth to fifth months of pregnancy.

hyperemesis). Sometimes there is an increase in blood pressure along with protein in the urine. Blood tests will show very high levels of human chorionic gonadotropin (hCG).[6]

Cause

The cause of this condition is not completely understood. Potential risk factors may include defects in the egg, abnormalities within the

folic acid, and carotene.[7] The diploid set of sperm-only DNA means that all chromosomes have sperm-patterned methylation suppression of genes. This leads to overgrowth of the syncytiotrophoblast whereas dual egg-patterned methylation leads to a devotion of resources to the embryo, with an underdeveloped syncytiotrophoblast. This is considered to be the result of evolutionary competition, with male genes driving for high investment into the fetus versus female genes driving for resource restriction to maximise the number of children.[8]

Pathophysiology

A hydatidiform mole is a pregnancy/

spontaneous abortion
(miscarriage).

Based on

fetal development is present. In partial moles, some villi are vesicular, whereas others appear more normal, and embryonic/fetal development may be seen but the fetus is always malformed and is never viable.

Uterus with complete hydatidiform mole

In rare cases, a hydatidiform mole co-exists in the uterus with a normal, viable fetus. These cases are due to

twinning. The uterus contains the products of two conceptions: one with an abnormal placenta and no viable fetus (the mole), and one with a normal placenta and a viable fetus. Under careful surveillance, it is often possible for the woman to give birth to the normal child and to be cured of the mole.[9]

Parental origin

In most complete moles, all

mitochondrial
genes are inherited from the mother, as usual.

Most partial moles are

fertilization of the egg.[10]

In rare cases, hydatidiform moles are

tetraploid
(four chromosome sets) or have other chromosome abnormalities.

A small percentage of hydatidiform moles have biparental diploid genomes, as in normal living persons; they have two sets of chromosomes, one inherited from each biological parent. Some of these moles occur in women who carry mutations in the gene NLRP7, predisposing them towards molar pregnancy. These rare variants of hydatidiform mole may be complete or partial.[11][12][13]

Diagnosis

Transvaginal ultrasonography
showing a molar pregnancy
Molar pregnancy in ultrasound
Hydatidiform mole on CT, sagittal view
Hydatidiform mole on CT, axial view

The diagnosis is strongly suggested by

sonogram), but definitive diagnosis requires histopathological examination. On ultrasound, the mole resembles a bunch of grapes ("cluster of grapes" or "honeycombed uterus" or "snow-storm").[14] There is increased trophoblast proliferation and enlarging of the chorionic villi, and angiogenesis in the trophoblasts is impaired.[15]

Sometimes symptoms of hyperthyroidism are seen, due to the extremely high levels of hCG, which can mimic the effects of thyroid-stimulating hormone.[15]

Complete Mole Partial Mole
Karyotype[16] 46,XX or 46,XY 69,XXY or 69, XXX
hCG ↑↑↑↑ ↑
Uterine Size ↑ –[clarification needed]
Fetal Parts No Yes
Components[16] 2 sperm + empty egg

or Empty egg + 1 sperm that duplicates

2 sperm + 1 egg

or 1 sperm + 1 egg that duplicates

Risk of Choriocarcinoma[17] 15% 0.5%

Treatment

Hydatidiform moles should be treated by evacuating the uterus by uterine suction or by surgical

antigens
, the response to treatment is nearly 100%. Patients are advised not to conceive for half a year after hCG levels have normalized. The chances of having another molar pregnancy are approximately 1%.

Management is more complicated when the mole occurs together with one or more normal fetuses.

In some women, the growth can develop into gestational trophoblastic neoplasia. For women who have complete hydatidiform mole and are at high risk of this progression, evidence suggests giving prophylactic chemotherapy (known as P-chem) may reduce the risk of this happening.[19] However P-chem may also increase toxic side effects, so more research is needed to explore its effects.[19]

Anesthesia

The uterine curettage is generally done under the effect of anesthesia, preferably spinal anesthesia in hemodynamically stable patients. The advantages of spinal anesthesia over general anesthesia include ease of technique, favorable effects on the pulmonary system, safety in patients with hyperthyroidism and non-tocolytic pharmacological properties. Additionally, by maintaining patient's consciousness one can diagnose the complications like uterine perforation, cardiopulmonary distress and thyroid storm at an earlier stage than when the patient is sedated or is under general anesthesia.[20]

Prognosis

More than 80% of hydatidiform moles are

contraception are recommended to avoid pregnancy for at least 6 to 12 months. Women who have had a prior partial or complete mole have a slightly increased risk of a second hydatidiform mole in a subsequent pregnancy, meaning a future pregnancy will require an earlier ultrasound scan.[21]

In 10 to 15% of cases, hydatidiform moles may develop into invasive moles. This condition is named

hemorrhage or other complications develop. It is for this reason that a post-operative full abdominal and chest X-ray
will often be requested.

In 2 to 3% of cases, hydatidiform moles may develop into choriocarcinoma, which is a malignant, rapidly growing, and metastatic (spreading) form of cancer. Despite these factors which normally indicate a poor prognosis, the rate of cure after treatment with chemotherapy is high.

Over 90% of women with malignant, non-spreading cancer are able to survive and retain their ability to conceive and bear children. In those with metastatic (spreading) cancer, remission remains at 75 to 85%, although their childbearing ability is usually lost.

Epidemiology

Hydatidiform moles are a rare complication of pregnancy, occurring once in every 1,000 pregnancies in the US, with much higher rates in Asia (e.g. up to one in 100 pregnancies in Indonesia).[4]

Etymology

The etymology is derived from hydatisia (Greek "a drop of water"), referring to the watery contents of the cysts, and mole (from Latin mola = millstone/false conception).[22] The term, however, comes from the similar appearance of the cyst to a hydatid cyst in an echinococcosis.[23]

References

  1. ^ "About molar pregnancy | Gestational trophoblastic disease (GTD) | Cancer Research UK". www.cancerresearchuk.org. Retrieved 18 June 2022.
  2. Merriam Webster
    . Retrieved May 7, 2012.
  3. ^
    ISBN 978-1-4377-0792-2
    .
  4. ^
    PMID 9443567
    .
  5. ISBN 0-7216-0187-1
    .
  6. ISBN 0-07-144159-X
    .
  7. ^ MedlinePlus Encyclopedia: Hydatidiform mole
  8. PMID 17413849
    .
  9. S2CID 33752037
    .
  10. ISBN 0-340-81662-7
    .
  11. PMID 1674641
    .
  12. S2CID 1417706
    .
  13. S2CID 32421323
    . Review.
  14. S2CID 6572375
    .
  15. ^ a b "The 6 questions that pregnant women should be ask to the doctor". HealthGuru. 15 March 2019.
  16. ^
    PMID 29083593
    , retrieved 2024-01-16
  17. PMID 26566410
    .
  18. ISBN 0-7216-0187-1
    .
  19. ^
    PMID 28892119
    .
  20. PMID 22223914
    .
  21. ^
    PMID 22439034
    .
  22. ^ Entries HYDATID n. (a.) and MOLE, n.6 in the Oxford English Dictionary online. (http://dictionary.oed.com/ — subscription required.)
  23. ^ "Hydatidiform".

External links

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