Hydatidiform Mole with Coexistant Viable Fetus

Introduction

Ahydatidiform mole with a coexistent live fetus is a rare entity with an incidence of 1:10,000 to 1:100,000. ¹ Diagnosis is usually made antenatally by ultrasonography (US) and confirmed by both macroscopic and microscopic evaluation of the products of conception. A hydatidiform mole can be a complete mole, a partial mole, or a triploid mole coexisting with a live fetus. Complete moles are androgenetic in origin, and the moles generally result from dispermy and reveal a triploid karyotype. A complete mole together with a coexistent viable fetus (CMCF) is extremely rare. In CMCF, the fetus is viable and places the obstetrician in a dilemma regarding management of the case. The actual risk of continuation of pregnancy in CMCF remains uncertain because of its rarity. This article presents a case of CMCF diagnosed at 14 weeks' gestation.

Case

A 30 year-old-woman, gravida 4, para 2, presented at 14 weeks' gestation to the obstetrics emergency unit with a history of bleeding per vaginum for 10 days. The bleeding was mild previously, but, on the day she came in to the emergency unit, she had heavy bleeding, which made her seek medical attention. No other significant history could be elicited from her.

On examination, she was alert and oriented, her vital signs were stable, and she did not have pallor. A breast and thyroid examination revealed no abnormalities. An abdominal examination revealed a gravid uterus corresponding to 18 weeks' gravid uterus size. At the time of her admission, a laboratory analysis revealed a hemoglobin (Hb) of 13 g% and a total leukocyte count of 12,200/mm³. Her platelet count, coagulation profile, and liver and renal function testing revealed no abnormalities. Ultrasonography (US), however revealed a single live fetus with a placenta in the uterine fundus, measuring 12×10×9 cm, with a heterogeneous lesion and many anechoic areas. The patient's ovaries appeared to be normal, so the US impression was one of a hydatidiform mole with a coexistent viable fetus (Fig. 1). Her serum β–human chorionic gonadotropin (β-hCG) at the time of admission was 564,836 IU/mL. The magnitude of the problem was discussed with the patient. She opted for termination of pregnancy, underwent induction of abortion with oxytocin, and spontaneously expelled a male abortus along with molar tissue and a normal-appearing placenta. The abortus and placenta together weighed 200 g and the molar tissue weighed 500 g. The abortus had no obvious congenital malformations. The patient's postabortal period was apparently uneventful. Histopathology of the products of conception was consistent with a normal placenta, a complete mole, and a fetus with no congenital malformations on autopsy. A week after abortion the patient's serum β-hCG level fell to 357 IU/mL, and this level normalized at 5 weeks postabortion. During the follow-up period, there was no evidence of persistent gestational trophoblastic disease (GTD).

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FIG. 1.

Real-time mode ultrasonography showing hydatidiform mole with coexistent fetus.

Discussion

A hydatidiform mole with a coexistent live fetus is a rare entity, with a reported incidence ranging from 1 in 10,000 to 1 in 100,000. ¹ Vassilakos et al. first described two distinct pathologic entities—partial and complete—with different mechanism of origin based on cytogenetic analysis. ² A pregnancy with a complete mole coexistent with a viable fetus carries a significant risk of severe complications, such as hyperemesis, hyperthyroidism, preeclampsia, and preterm delivery (either spontaneous or induced). ³ Theca lutein cysts and ascites have been reported. ⁴

Diagnosis is done by US, a with reported sensitivity of 68%. ⁵ At times, abnormal placental echoes may be misinterpreted as being a hematoma. ⁶ Markedly elevated hCG levels may suggest CMCF. Recent studies have suggested that immunohistochemical staining with p57^KIP2 can be used to distinguish androgenetic conceptuses from biparental ones. ⁷ Mesenchymal dysplasia (a pseudopartial mole) is a rare condition of pregnancy that presents as a macroscopic feature of molar change in the placenta and a normal-karyotype fetus. This entity is often misdiagnosed as a partial mole; the key distinctive feature is the absence of trophoblastic invasion in mesenchymal dysplasia. ⁸

Whenever a diagnosis of CMCF pregnancy is suspected, a karyotype of the coexistent fetus should be obtained. The success rate of pregnancy with a normal karyotype is only 25%, with known consequences of preterm delivery and prematurity. ⁹ Thus, it remains controversial whether to continue such a pregnancy or to terminate it irrespective of karyotype because a complete mole carries a higher risk for the patient of developing persistent GTD. In the presence of a normal karyotype and the absence of maternal complications, continuation of pregnancy has been suggested by few researchers, because they suggest that the risk of persistent trophoblastic disease is similar to that of singleton molar pregnancies in complete mole with coexisting fetus pregnancy.^10–12 In cases of coexistent partial mole, the fetus is always triploid and therefore termination of pregnancy is indicated. ⁹ Termination of pregnancy can be achieved by suction evacuation, dilatation and evacuation, or oxytocin infusion. Use of prostaglandins is avoided because of the increased risk of complications and malignant sequelae. ¹³

Careful follow-up is warranted, as persistent GTD may develop in 12%–20% of patients who have had singleton pregnancies with CMCF against 1%–5% of patients who have had pregnancies with with partial moles. ⁵ Low-dose oral contraceptive pills can be prescribed safely during the follow-up period.

Conclusions

A hydatidiform mole coexistent with a viable fetus is a rare entity with a poor prognosis. Continuation of pregnancy in CMCF is controversial because of the risk of maternal complications and risk of persistent GTD.