AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Background

Vanishing twin syndrome, first described by Stoeckel in 1945, is the identification of a multifetal gestation with subsequent disappearance of one or more fetuses. The rate of multifetal gestation at conception is higher than the incidence noted at birth. Vanishing twin syndrome has been diagnosed more frequently since the use of ultrasonography in early pregnancy. In vitro fertilization techniques have improved the understanding of vanishing twin syndrome because these pregnancies are closely monitored, and the number of implanted fertilized eggs is known.

In vanishing twin syndrome, there may be complete reabsorption of a fetus, formation of a fetus papyraceus (ie, a "mummified" or compressed fetus), or development of a subtle abnormality on the placenta such as a cyst, subchorionic fibrin, or amorphous material.

The timing of this event significantly affects the outcome of the viable twin and the maternal complications. For example, if the event occurs during the first trimester, neither the remaining fetus nor the mother should have any untoward effects; however, if the event occurs during the second half of pregnancy, the fetus could develop cerebral palsy or cutis aplasia, and the mother could develop preterm labor, infection, puerperal hemorrhage, consumptive coagulopathy, or obstruction of labor.

Pathophysiology

Abnormalities that result in the disappearance of a fetus usually appear to be present from early in development rather than occurring from an acute insult. Placental or fetal analysis frequently reveals chromosome abnormalities. Study findings of the viable twin are usually normal. Therefore, it is thought that the vanished twin had a chromosomal abnormality or syndrome that resulted in disappearance.

Frequency

United States

The frequency of multiple gestations is 3.3-5.4% at 8 weeks' gestation. Vanishing twin syndrome occurs in 21-30% of multifetal gestation.

Research from a European series of pregnancies associated with assisted reproductive technology (ART) show that 10-15% of singleton births were initially twin gestations.

International

International prevalence is similar to that of the United States.

Mortality/Morbidity

• First trimester: Morbidity when vanishing twin syndrome occurs during the first trimester is limited. The mother is most likely to develop mild vaginal bleeding and cramping. If the event occurs later in the first trimester, morbidity may be similar to that of the second and third trimesters.
• Second and third trimesters: Maternal complications include premature labor, infection from a retained fetus, severe puerperal hemorrhage, consumptive coagulopathy, and obstruction of labor by a low-lying fetus papyraceus causing dystocia and leading to a cesarean delivery.
• The diagnosis of vanishing twin in a pregnancy significantly increases both preterm (<37 gestational weeks) and very preterm (<32 gestational weeks) births.
• Fetal morbidity and mortality
• • In addition to loss of a twin, the surviving fetus has an increased risk of cerebral palsy, particularly if vanishing twin syndrome occurred during the second half of pregnancy.¹
  • Other forms of morbidity reported in the surviving twin are aplasia cutis or areas of skin necrosis. In twins connected through vascular connection by placental anastomoses, temporary hypotension in the surviving twin at the time of fetal demise of the vanishing twin leads to poor perfusion and skin necrosis.

Race

No predilection for any race has been reported.

Sex

No predilection for either sex has been reported in the vanishing twin.

Age

Researchers report more cases in women older than 30 years. Advanced maternal age is also a recognized risk factor for fetal and placental chromosome abnormalities.

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

History

Problems usually develop during the first trimester of pregnancy. The most common presenting complaints include bleeding, uterine cramps, and pelvic pain.

Physical

Vaginal bleeding may be observed on pelvic examination.

Causes

The cause of vanishing twin syndrome is frequently unknown; however, this condition occurs more often in fetuses with genetic or chromosomal abnormalities. Improper cord implantation may also play a role in some cases.

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

• Threatened abortion
• Decidual reaction on sonogram
• Amniotic cavity observed on sonogram as a second fetus
• Chorionic sac observed on sonogram as a second fetus
• Yolk sac or extraembryonic coelom observed on sonogram as a second fetus
• Subchorionic hemorrhage or hydropic change in chorionic villi observed on sonogram as a second fetus

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Lab Studies

• Alpha-fetoprotein levels are elevated compared with values at similar junctures in both a singleton pregnancy and a normal twin pregnancy.
• The rate of rise of beta-human chorionic gonadotropin is slower than in a normal twin pregnancy.

Imaging Studies

Ultrasonography is used to confirm the diagnosis of early twin pregnancy. Follow-up ultrasonography reveals the pregnancy loss (vanishing twin).

Other Tests

Amniocentesis after diagnosis of a vanishing twin by prior ultrasound has been reported to detect an XY cell by both FISH and real-time PCR in the sustained XX 20 weeks' gestation pregnancy. The authors caution about interpretation of amniocentesis results because a vanishing twin fetus could lead to false-positive results.

Procedures

• After diagnosing first-trimester bleeding, using ultrasonography before dilation and curettage is important. This ensures that bleeding does not signal the loss of just one fetus.
• Chorionic villus sampling may be helpful if the placenta has a mosaic makeup and there is a singleton at birth.

Histologic Findings

Obtain histological samples of the placenta at birth since they may be the only evidence of vanishing twin syndrome with a reabsorbed fetus.

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical Care

• If a fetus papyraceus remains, the pregnancy should be followed closely with serial ultrasonographic evaluation of the live fetus. Risks include premature labor or death of the surviving fetus due to placental abruption or chorioamnionitis. This fetus is also at risk for intrauterine growth restriction.
• The provider should watch carefully for infection and consumptive coagulopathy.
• Uncomplicated vanishing twin syndrome requires no special medical care.

Surgical Care

Only perform dilation and curettage after ultrasound confirmation that a viable embryo or fetus does not exist.

FOLLOW-UP

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

The viable twin should receive specialized medical care as indicated by initial physical examination and subsequent mental and physical development.

Further Outpatient Care

Pharoah's group reported in 2007 that surviving cotwins had similar scores when compared with singleton pregnancies on Griffiths Mental and Development Scales.²

Transfer

Evaluate pregnant women with vaginal bleeding at a site with adequate ultrasonographic capabilities.

Complications

• Cerebral palsy
• • Researchers recently proposed that vanishing twin syndrome could result in spastic cerebral palsy in the remaining twin. (Cerebral palsy is the most common hypothesized pathological clinical sequela in the viable twin.)
  • A possible mechanism is the transfusion of thromboplastic proteins from the vanishing twin to the surviving twin, leading to disseminated intravascular coagulation (DIC). Researchers hypothesize that DIC results from reverse blood flow from the macerated twin to the viable twin, thus carrying thromboplastins into the circulation. This large thromboplastin load is hypothesized to lead to a state of DIC in the viable twin, which then leads to intrauterine central nervous system damage.
  • Another proposed mechanism for central nervous system damage involves large amounts of blood loss from the surviving twin to the low resistance system of the vanishing twin through placental anastomoses. This transfusion could cause wide fluctuation in intravascular pressures, leading to intraventricular hemorrhage that results in cerebral palsy.
• Associated congenital anomalies 
• • A link in children with cerebral palsy and other congenital anomalies is possible. In one series, the relative risk for congenital malformations, including microcephaly, isolated hydrocephaly, eye, cleft lip/palate, and cardiac anomalies, increased over baseline from relative risk 3.1-116 (95% CI, 1.9-4.8 to 84 to 162.3; P<0.01 to P<0.0001) depending on the specific defect. These anomalies are postulated to be due in part to perturbations in fetal flow in the surviving twin at the time of loss of the vanishing twin.
• Cutis aplasia
• • The mechanism of development of cutis aplasia is most likely vascular, with decreased perfusion to the affected area around the demise of the vanished twin, who in this case was a fetus papyraceous.³

Patient Education

Instruct pregnant women to seek medical care for vaginal bleeding, cramping, and pelvic pain.

MISCELLANEOUS

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Do not perform dilation and curettage until certain that no viable fetus remains.
• If chorionic villus sampling is performed during a multifetal gestation, be aware that a mosaic placenta may be present. A viable fetus with normal chromosomes may be supported by the placenta of a vanished twin with abnormal chromosomes.
• The full implications of fertility treatments that involve implantation of multiple eggs with reabsorption of several during the course of the pregnancy are unknown.

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

1. Pharoah PO, Cooke RW. A hypothesis for the aetiology of spastic cerebral palsy--the vanishing twin. Dev Med Child Neurol. May 1997;39(5):292-6. [Medline].
2. Pharoah PO. Prevalence and pathogenesis of congenital anomalies in cerebral palsy. Arch Dis Child Fetal Neonatal Ed. Nov 2007;92(6):F489-93. [Medline].
3. Classen DA. Aplasia cutis congenita associated with fetus papyraceous. Cutis. Aug 1999;64(2):104-6. [Medline].
4. Abbas A, Johnson M, Bersinger N, Nicolaides K. Maternal alpha-fetoprotein levels in multiple pregnancies. Br J Obstet Gynaecol. Feb 1994;101(2):156-8. [Medline].
5. Anand D, Platt MJ, Pharoah PO. Comparative development of surviving co-twins of vanishing twin conceptions, twins and singletons. Twin Res Hum Genet. Feb 2007;10(1):210-5. [Medline].
6. Anand D, Platt MJ, Pharoah PO. Vanishing twin: a possible cause of cerebral impairment. Twin Res Hum Genet. Feb 2007;10(1):202-9. [Medline].
7. Benirschke K. Intrauterine death of a twin: mechanisms, implications for surviving twin, and placental pathology. Semin Diagn Pathol. Aug 1993;10(3):222-31. [Medline].
8. Blumenfeld Z, Dirnfeld M, Abramovici H, et al. Spontaneous fetal reduction in multiple gestations assessed by transvaginal ultrasound. Br J Obstet Gynaecol. Apr 1992;99(4):333-7. [Medline].
9. Bryan E. Loss in higher multiple pregnancy and multifetal pregnancy reduction. Twin Res. Jun 2002;5(3):169-74. [Medline].
10. Jauniaux E, Elkazen N, Leroy F, et al. Clinical and morphologic aspects of the vanishing twin phenomenon. Obstet Gynecol. Oct 1988;72(4):577-81. [Medline].
11. Kelly MP, Molo MW, Maclin VM, Binor Z, Rawlins RG, Radwanska E. Human chorionic gonadotropin rise in normal and vanishing twin pregnancies. Fertil Steril. Aug 1991;56(2):221-4. [Medline].
12. Landy HJ, Keith LG. The vanishing twin: a review. Hum Reprod Update. Mar-Apr 1998;4(2):177-83. [Medline].
13. Landy HJ, Weiner S, Corson SL, et al. The "vanishing twin": ultrasonographic assessment of fetal disappearance in the first trimester. Am J Obstet Gynecol. Jul 1986;155(1):14-9. [Medline].
14. Lau WC, Rogers MS. Fetus papyraceous: an unusual cause of obstructed labour. Eur J Obstet Gynecol Reprod Biol. Sep 1999;86(1):109-11. [Medline].
15. Newton R, Casabonne D, Johnson A, Pharoah P. A case-control study of vanishing twin as a risk factor for cerebral palsy. Twin Res. Apr 2003;6(2):83-4. [Medline].
16. Pinborg A, Lidegaard O, Andersen AN. The vanishing twin: a major determinant of infant outcome in IVF singleton births. Br J Hosp Med (Lond). Aug 2006;67(8):417-20. [Medline].
17. Pinborg A, Lidegaard O, la Cour Freiesleben N, Andersen AN. Consequences of vanishing twins in IVF/ICSI pregnancies. Hum Reprod. Oct 2005;20(10):2821-9. [Medline].
18. Rudnicki M, Vejerslev LO, Junge J. The vanishing twin: morphologic and cytogenetic evaluation of an ultrasonographic phenomenon. Gynecol Obstet Invest. 1991;31(3):141-5. [Medline].
19. Saidi MH. First-trimester bleeding and the vanishing twin. A report of three cases. J Reprod Med. Oct 1988;33(10):831-4. [Medline].
20. Sulak LE, Dodson MG. The vanishing twin: pathologic confirmation of an ultrasonographic phenomenon. Obstet Gynecol. Dec 1986;68(6):811-5. [Medline].
21. Verstraete L, Costa JM, Chantot-Bastaraud S, Siffroi JP, Fiori O, Uzan S. Finding a single XY cell among XX cells in amniotic fluid by FISH: a possible consequence of a vanishing male twin?. Prenat Diagn. Jan 2007;27(1):85-6. [Medline].

Article Last Updated: Dec 10, 2007