Twin mole and viable fetus: The case for misdiagnosis

To report the Sheffield Trophoblast Centre experience of twin molar gestations and review this in the light of international experience.

Thirty patients with possible twin molar gestations were registered from 1986 to 2004 (during which period 7,200 cases of mole were seen). The accuracy of suspected clinical and histologic diagnoses was investigated.

In 10 cases twin mole/fetus had been suspected clinically but not confirmed when products of conception were examined. In 3 of these cases the pregnancy had been therapeutically terminated because of clinical (ultrasound) suspicion of coexisting molar pregnancy. In the 19 cases where twin mole/fetus was suspected, central histopathology review was possible in 14 cases. Only 7 were confirmed. In 2 further cases twin molar gestation was diagnosed on specimens referred for central review as partial mole singleton pregnancies. For confirmed cases the pregnancy outcome was term delivery in 5 cases and miscarriage in 4.

Clinical and histopathologic diagnosis of twin molar pregnancies is inaccurate in many suspected cases; therefore, a second (expert) opinion should be sought. When the diagnosis is accurate, maternal and fetal complications are common. However, in suspected cases the pregnancy may be allowed to proceed, with caution, if the mother wishes.