[1] Florianopolis, SC Brazil, [2] Sao Paulo — SP [3] Nashville, TN jeanty@pov.net

Adapted and reproduced with permission from TKI Medcon Inc. http:/www.tki.com/

Definition

First trimester loss of a member of a twin gestation.

Sonographic features

Small gestational sac with a fetus whose development lags compared to the other fetus. No fetal heart activity can be detected. The spectrum varies from a crescent-shaped sac adjacent to a normal early gestation (up to 10-14 weeks) to a well-formed but dead fetus (fetus papyraceus). Early vanishing twins should be distinguished from implantation bleeds that are not surrounded by a trophoblastic ring.

An ill-defined gestational sac that could easily appear to be an implantation bleed, although some agonal flow still go to the embryo.

The five image above are from a triplet pregnancy (trichorionic). On the first image the smallest gestational sac is visible. It contains no embryo. The left sac contains an embryo with no heart beat. The lower sac contains a live embryo.

Dichorionic diamniotic gestational sacs. On the first image, there is no evidence of an embryo, the second image obtained a week later, demonstrates normal growth one one embryo and elimination of the other sac.

At 16 weeks, the sac of a vanishing twins can sometimes still be visible.

17-weeks. A fetus papyraceus (first image) and the normal co-twin.

Differential diagnosis

The differential diagnosis includes implantation bleeds in the early pregnancy and chorioangioma as well placental cysts after the second trimester. Chorioangioma is the most important entity in the differential diagnosis because of its known relationship to nonimmune hydrops as well as preeclampsia. The lack of blood flow on color Doppler, excludes the diagnosis of chorioangioma.

Associated syndromes

Fetus papyraceus. This is a macerated fetus delivered with a normal co-twin, and usually embedded in the placental membranes.

References

1. Saier F, Burden L, Cavanagh D. Fetus papyraceus: an unusual case with congenital anomaly of the surviving fetus. Obstet Gynecol 1975; 45:217.
2. Benirschke K. Intrauterine death of a twin: Mechanisms, implications for surviving twin, and placental pathology. Semin Diagn Pathol 1993;10:222.
3. Posner AC, Klein, MA. Fetus payraceus. Recognition and significance. Obstet Gynecol 1954;3:106. 4. Levi S, Reimers M. Demonstration echographique de la frequence relativement elevee des grossesses multiples humaines pendant la periode embryonnaire. L"implantation de L"oeuf. Paris, Masson, 1978, pp 295-307.
4. Varma TR: Ultrasound evidence of early pregnancy failure in patients with multiple conceptions. Br J Obstet Gynaecol 1979; 86:290.
5. Jeanty P, Rodesch F, Struyven J: The vanishing twin. J Belge Radiol 1982;63: 526.
6. Landy HJ, Deith L, Deith D. The vanishing twin. Acta Genet Med Gemellol (Roma)1982;31:179.
7. Levi S: Ultrasonic assessment of the high rate of human multiple pregnancy in the first trimester. J C U 1976;4:3.
8. Robinson HP, Caines JS: Sonar evidence of early pregnancy failure in patients with twin conceptions. Br J Obstet Gynaecol 1977;84: 22.
9. Landy HJ, Weiner S, Corson SL,et al: The "vanishing twin": Ultrasonographic assessment of fetal disappearance in the first trimester. Am J Obstet Gynecol 1986;155:14.
10. Sulak LE, Dodson MG: The vanishing twin: pathologic confirmation of an ultrasonographic phenomenon. Obstet Gynecol 1986;68: 811.