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Complete Hydatidiform Mole with a Coexisting Twin Fetus (CHMTF) refers to a rare condition in which a complete molar pregnancy coexists in the uterus with a viable or non-viable live fetus.

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It is a form of twin pregnancy comprising:

One normal fetus with a normal placenta
One complete hydatidiform mole (CHM) — i.e., diploid tissue derived entirely from paternal origin, with no embryonic tissue and diffuse villous hydropic degeneration

![Schematic showing three types of molar pregnancies with coexisting fetus: (A) is a depiction of a twin pregnancy with both a complete mole and a normal fetus. Of the three possibilities this is the most common, although overall this entity is very rare. Given the diploid fetus and diploid complete mole, all karyotypes in this entity should be diploid. (B) depicts a singleton pregnancy in which a partial mole is present with a likely growth restricted, non-viable, and triploid fetus. (C) is the least common of the three and depicts a twin pregnancy with one partial mole displaying some fetal parts and a co-twin normal fetus. This schematic was illustrated by author M.L.

Lemieux M, Kus L, Stewart K, et al. Complete Hydatidiform Mole with a Coexisting Viable Male Fetus Detected by Cell-Free DNA. American Journal of Perinatology Reports. 2023;13(03):e49-e52. doi:https://doi.org/10.1055/s-0043-1774727](attachment:edb60645-ff61-4824-8cf2-47dca0b1776c:10-1055-s-0043-1774727-i23jul0014-2.jpg)

Schematic showing three types of molar pregnancies with coexisting fetus: (A) is a depiction of a twin pregnancy with both a complete mole and a normal fetus. Of the three possibilities this is the most common, although overall this entity is very rare. Given the diploid fetus and diploid complete mole, all karyotypes in this entity should be diploid. (B) depicts a singleton pregnancy in which a partial mole is present with a likely growth restricted, non-viable, and triploid fetus. (C) is the least common of the three and depicts a twin pregnancy with one partial mole displaying some fetal parts and a co-twin normal fetus. This schematic was illustrated by author M.L.

Epidemiology

Incidence: ~1 in 20,000 to 100,000 pregnancies
Increased frequency with assisted reproductive techniques (ART)
Significantly rarer than partial mole

Pathophysiology

Arises due to simultaneous fertilization of two ova:
- One becomes a normal fetus with normal karyotype
- The other becomes a complete mole (usually 46,XX from androgenesis)
Both gestations implant and develop simultaneously

![Genetic basis for development of normal pregnancy and complete hydatidiform mole: In aberration of the normal process of fertilization, at times, one or even two sperms fertilize an empty ovum. The fertilized egg (zygote) therefore contains only paternal DNA along with maternal mitochondria. This divides and subdivides to form a complete hydatidiform mole (CHM) pregnancy with no embryo development (46XX or 46XY-diploidy)

Bajaj, S.K., Misra, R., Gupta, R. et al. Complete Hydatidiform Mole with Coexisting Twin Fetus: Usefulness of MRI in Management Planning. J Obstet Gynecol India 64 (Suppl 1), 9–13 (2014). https://doi.org/10.1007/s13224-012-0346-2](attachment:9c66e570-f590-43c9-84ef-e4b75da7160a:13224_2012_346_Fig3_HTML.webp)

Genetic basis for development of normal pregnancy and complete hydatidiform mole: In aberration of the normal process of fertilization, at times, one or even two sperms fertilize an empty ovum. The fertilized egg (zygote) therefore contains only paternal DNA along with maternal mitochondria. This divides and subdivides to form a complete hydatidiform mole (CHM) pregnancy with no embryo development (46XX or 46XY-diploidy)

![Genetic basis for development of partial hydatidiform mole and complete H mole with coexistent twin fetus: In yet another situation, a dizygotic pregnancy occurs where a CHM develops side by side with a normal twin embryo. Here, the embryo is single, but the placentae are two—one molar and the other normal

Bajaj, S.K., Misra, R., Gupta, R. et al. Complete Hydatidiform Mole with Coexisting Twin Fetus: Usefulness of MRI in Management Planning. J Obstet Gynecol India 64 (Suppl 1), 9–13 (2014). https://doi.org/10.1007/s13224-012-0346-2](attachment:bf046552-c27b-45ef-8eda-3238a3d25560:13224_2012_346_Fig4_HTML.webp)

Genetic basis for development of partial hydatidiform mole and complete H mole with coexistent twin fetus: In yet another situation, a dizygotic pregnancy occurs where a CHM develops side by side with a normal twin embryo. Here, the embryo is single, but the placentae are two—one molar and the other normal

Gross sample:

![Photograph of the abortus showing a dead fetus with the normal cord and placenta. The complete hydatidiform molar mass with bunch of grapes appearance is seen alongside

Bajaj, S.K., Misra, R., Gupta, R. et al. Complete Hydatidiform Mole with Coexisting Twin Fetus: Usefulness of MRI in Management Planning. J Obstet Gynecol India 64 (Suppl 1), 9–13 (2014). https://doi.org/10.1007/s13224-012-0346-2](attachment:097c582a-5ea6-4c8b-8609-c64cc74ee1fa:13224_2012_346_Fig5_HTML.webp)

Photograph of the abortus showing a dead fetus with the normal cord and placenta. The complete hydatidiform molar mass with bunch of grapes appearance is seen alongside

![(A) shows ultrasound findings at gestational age 19w3d highlighting the highly vascular molar-appearing tissue in the uterus. (B–E) Placental pathology from the molar appearing placenta. Enlarged chorionic villi are seen with empty stroma (cistern formation) with no fetal capillaries or fetal red blood cells. (B) shows a tissue sample with p57 stain. (C) shows extravillous trophoblasts stained p57 positive as an internal control. (D) shows villous cytotrophoblast that are p57 negative from the molar appearing villi. (E) shows villous stromal cells that are p57 negative from the molar appearing villi.

Lemieux M, Kus L, Stewart K, et al. Complete Hydatidiform Mole with a Coexisting Viable Male Fetus Detected by Cell-Free DNA. American Journal of Perinatology Reports. 2023;13(03):e49-e52. doi:https://doi.org/10.1055/s-0043-1774727](attachment:68cdd856-b49c-41c1-b8b6-19e3127a0550:eacc01fd-462c-4e94-8519-c3d113d756f5.png)

(A) shows ultrasound findings at gestational age 19w3d highlighting the highly vascular molar-appearing tissue in the uterus. (B–E) Placental pathology from the molar appearing placenta. Enlarged chorionic villi are seen with empty stroma (cistern formation) with no fetal capillaries or fetal red blood cells. (B) shows a tissue sample with p57 stain. (C) shows extravillous trophoblasts stained p57 positive as an internal control. (D) shows villous cytotrophoblast that are p57 negative from the molar appearing villi. (E) shows villous stromal cells that are p57 negative from the molar appearing villi.

Clinical features

Vaginal bleeding (common presenting symptom)