Complete molar pregnancy and coexisting live fetus

Case contributed by Dr Alexandra Stanislavsky


G1PO at 28+4/40 with threatened pre-term labor. 20 week ultrasound performed elsewhere showed normal morhology but possible caudal placental extension covering os.

Patient Data

Age: 35 years
Gender: Female

Small for gestational age fetus with AC on the 10th centile and EFW on the 7th. No morphologic abnormality was seen, and the AFI and Dopplers were normal.

Directly caudal to the normal placental tissue, there is abnormal heterogeneous tissue with multiple cystic spaces and small amount of vascularity. It contacts the placenta at the margin but appears to be separate from it, and it wraps around the lower uterine cavity, covering the internal os. The interface between the normal placenta and abnormal tissue is shown in the second image stack.

The cervix is closed.

The appearance was highly unusual, and the differentials considered at this stage included uncommon conditions, including late-stage diagnosis of partial or concurrent molar pregnancy, partially hydropic placenta with placenta previa (though it would be exceedingly unlikely for a single placenta to have such varied appearances) or placental mesenchymal dysplasia.

Amniocentesis was performed showing a normal karyotype.

The baby remained small for gestational age but continued to grow appropriately, and the periplacental tissue remained unchanged.   The baby was delivered by Caesarean section at 36w2d in good condition requiring no resuscitation, with a birth weight of 2.3kg.  

Pathology report excerpt (placenta):

... Sharply demarcated from the normal villi are chorionic villi which show marked hydropic swelling with cistern formation. They have scalloped shaped outline and abnormal circumferential florid trophoblastic proliferation. There are focal piling up of syncytiotrophoblasts with large vacuoles. Cytotrophoblastic villous inclusions are seen. Stomal cell karyorrhexis is not a feature. p57 immunostain shows negative nuclear staining of the villous stromal cells and cytotrophoblasts but positive staining of the intermediate trophoblasts. Features are highly suspicious of a complete mole.



Case Discussion

This is a rare case of a twin pregnancy comprising a live fetus and a complete hydatidiform mole.

Case reports of this condition report a high rate of complications, including heavy PV bleeding, pre-eclampsia, intrauterine fetal death or growth restriction and pre-term birth. In this case there was mild IUGR and prematurity but no other early fetal or maternal complications.

The mother will undergo ongoing monitoring for recurrence of gestational trophoblastic disease.

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Case information

rID: 61467
Published: 11th Jul 2018
Last edited: 5th Jan 2020
System: Obstetrics
Inclusion in quiz mode: Included

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