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Key Points

  • Intrauterine fetal death (IUFD) of one twin in the first trimester is common and is known as a “vanishing twin.”

  • Although a “vanishing twin” may be associated with vaginal spotting, it is not associated with adverse perinatal outcomes for the surviving twin.

  • Single IUFD in the second and third trimester is less common and is more likely to be associated with complications for the surviving co-twin.

  • When single IUFD occurs in a monochorionic pregnancy, it is associated with a worse prognosis, including up to 20% incidence of significant neurologic morbidity for the surviving co-twin, such as multicystic encephalomalacia.

  • Sonographic assessment of a single IUFD in a twin pregnancy should include determination of chorionicity, the accuracy of which may be limited in the second and third trimesters.

  • If a certain diagnosis of chorionicity is needed for pregnancy management, DNA studies on amniocytes may be needed.

  • Management of a case of single IUFD depends on gestational age and chorionicity.

  • Preterm labor and delivery is often associated with single IUFD. Otherwise, expectant management is suggested if the gestational age is less than or equal to 37 completed weeks and there are no indications for delivery.

  • Surviving co-twins in a monochorionic pregnancy should be evaluated postnatally for neurologic sequelae.


The intrauterine fetal death (IUFD) ofone twin occurs most commonly during the first trimester. This phenomenon is known as a “vanishing twin” (Landy and Weingold, 1989). Although this may be associated with vaginal spotting, the loss of one conceptus is often not clinically recognized, and the prognosis for the surviving twin is excellent (Landy et al., 1986; Samuels, 1988; Prompeler et al., 1994).

Single IUFD in the second or third trimesters is much less common. Single IUFD is observed more often in association with monochorionic than with dichorionic placentation. When it occurs in a monochorionic gestation it may be associated with a worse outcome for the surviving co-twin.

The etiology of IUFD in a multiple pregnancy may be similar to singletons or unique to the twinning process. IUFD may be caused by genetic or anatomical anomalies, abruption, placental insufficiency, cord abnormalities such as a velamentous cord insertion, infection, and maternal disease including diabetes and hypertension (Ogunyemi et al., 1998; Collins, 2002; Craven and Ward, 2002; Simpson, 2002). In monochorionic pregnancies, IUFD may result from complications of the twin-to-twin transfusion syndrome (TTTS). Most often, the smaller, donor twin dies, but IUFD can occur in the larger recipient twin (D’Alton and Simpson, 1995). In addition, monoamniotic twins are at increased risk of cord entanglement and subsequent IUFD (Colburn and Pasquale, 1982). Similar to singletons, the etiology of IUFD often remains elusive (Santema et al., 1995).

Single IUFD in a multiple gestation can adversely affect the surviving fetus or fetuses in ...

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