AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

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

INTRODUCTION

Section 2 of 10  

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

Background

Twin-to-twin transfusion syndrome (TTTS) is the result of an intrauterine blood transfusion from one twin (donor) to another twin (recipient). TTTS only occurs in monozygotic (identical) twins with a monochorionic placenta. The donor twin is often smaller with a birth weight 20% less than the recipient's birth weight. The donor twin is often anemic and the recipient twin is often plethoric with hemoglobin differences greater than 5 g/dL.

Pathophysiology

TTTS is the result of transfusion of blood from one fetal twin to another twin. The blood transfusion from the donor twin to the recipient twin occurs through placental vascular anastomoses. The most common vascular anastomosis is a deep, artery-to-vein anastomosis through a shared placental cotyledon.

TTTS is a specific complication of monozygotic twins with monochorionic placentation. Although monozygotic twins can have dichorionic placentation, such twins are not at risk for TTTS. Monozygotic twins with monochorionic, diamniotic placentation (see Media File 1) or monochorionic, monoamniotic placentation are at risk for TTTS (see Media File 2).
 
The clinical features of TTTS are the result of hypoperfusion of the donor twin and hyperperfusion of the recipient twin.

The donor twin becomes hypovolemic and oliguric or anuric. Oligohydramnios develops in the amniotic sac of the donor twin. Profound oligohydramnios can result in the stuck twin phenomenon in which the twin appears in a fixed position against the uterine wall. Ultrasonography may fail to visualize the fetal bladder because of absent urine.

The recipent twin becomes hypervolemic and polyuric. Polyhydramnios develops in the amniotic sac of the recipient twin.

Either twin can develop hydrops fetalis. The donor twin can become hydropic because of anemia and high-output heart failure. The recipient twin can become hydropic because of hypervolemia. The recipient twin can also develop hypertension, hypertrophic cardiomegaly, disseminated intravascular coagulation, and hyperbilirubinemia after birth.

Frequency

United States

Monozygotic twins occur in 3-5 per 1000 pregnancies. Monozygotic twins can be monochorionic or dichorionic. Approximately 75% of monozygotic twins are monochorionic. Only monochorionic twins are at risk for TTTS. TTTS occurs in 5-38% of monochorionic twins.

Mortality/Morbidity

Severe TTTS has a 60-100% fetal or neonatal mortality rate. Mild-to-moderate TTTS is frequently associated with premature delivery. Fetal demise of one twin is associated with neurologic sequelae in 25% of surviving twins. Fetal blood pressure instability can lead to brain ischemia in either the donor or recipient twin. Ischemia of the fetal brain can result in periventricular leukomalacia, porencephaly, microcephaly and cerebral palsy. The more premature the twins are at birth, the higher the incidence of postnatal morbidity and mortality.

Sex

TTTS only occurs in same sex, monozygotic twins with monochorionic placentation.

CLINICAL

Section 3 of 10  

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

History

• Women with twin pregnancies who develop twin-to-twin transfusion syndrome (TTTS) frequently complain of a rapidly enlarging abdomen over 2-3 weeks as polyhydramnios develops in the amniotic sac of the recipient twin.
• Other complaints include preterm labor and premature rupture of membranes.

Physical

TTTS should be considered in a pregnant woman carrying twins if she develops a rapidly increasing fundal height. After birth, TTTS can be considered if the twins are monozygotic, and significant differences occur in the size or appearance of the twins. 

• Donor twin
• • Small for gestational age - More than 20% smaller than recipient twin
  • Pallor
  • Poor peripheral perfusion
• Recipient twin
• • Large for gestational age - More than 20% larger than donor twin
  • Plethoric and ruddy
  • Jaundice
• Hydrops fetalis can be present in either twin in TTTS. These infants have subcutaneous edema, a distended abdomen, and respiratory distress.

Causes

TTTS occurs in monozygotic, monochorionic twin pregnancies when an anastomosis between placental vasculature exists.

DIFFERENTIALS

Section 4 of 10  

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

Other Problems to be Considered

Hydrops fetalis
Polycythemia
Polycythemia of the newborn
Polyhydramnios
Oligohydramnios
Anemia of the newborn

WORKUP

Section 5 of 10  

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

Lab Studies

• Amniocentesis should be considered to test for aneuploidy and intrauterine infection.
• CBC count: The donor twin is frequently anemic at birth, whereas the recipient twin is frequently polycythemic at birth.
• Calcium: Hypocalcemia is frequently present in the donor twin.
• Glucose: Hypoglycemia may be present in either twin.
• Creatinine: Either twin may have evidence of renal dysfunction.
• Platelet count: Thrombocytopenia can occur in either twin.
• Bilirubin: Hyperbilirubinemia may develop in the polycythemic recipient twin.

Imaging Studies

• Sonographic findings of TTTS include the following:
• • Significant discrepancy in size of same-sex fetuses
  • Significant disparity in the amount of amniotic fluid between the fetuses with the smaller twin having oligohydramnios
  • Single placenta
• Neonatal brain ultrasonography: Because ischemia of the brain can occur during fetal development in either the donor or recipient twin, brain ultrasonography should be considered in both twins born with TTTS. Twins born prematurely are susceptible to intraventricular hemorrhage and periventricular leukomalacia.
• Neonatal echocardiography: Myocardial dysfunction, myocardial hypertrophy, valvular insufficiency, and pericardial effusions can be detected in either twin.
• Neonatal renal ultrasonography: Abnormal renal echogenicity may be present in either twin and indicates hypoxic-ischemic cortical necrosis.
• Neonatal abdominal ultrasonography: Ascites may be present if hydrops fetalis occurs.
• Neonatal chest radiography: Pleural effusions and cardiomegaly may be present if hydrops fetalis occurs.

Staging

The most useful staging system for TTTS was developed by Quintero:¹

Stage	Oligohydramnios/ Polyhydramnios	Absent Urine in Donor Bladder	Abnormal Doppler Blood Flows	Hydrops Fetalis	Fetal Demise
I	+	-	-	-	-
II	+	+	-	-	-
III	+	+	+	-	-
IV	+	+	+	+	-
V	+	+	+	+	+

 

TREATMENT

Section 6 of 10  

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

Medical Care

The most common procedure to treat TTTS is reduction amniocentesis. This procedure involves draining the amniotic fluid from around the recipient twin. This procedure may improve circulation in the donor twin.

Fetoscopic laser photocoagulation of chorionic plate vessels is a highly specialized procedure performed in a few centers around the world.

Medical care of twins after birth is directed toward problems related to prematurity, anemia, polycythemia, and hydrops fetalis.

• Severely anemic donor twins may require packed RBC transfusions or partial exchange transfusions.
• Polycythemic recipient twins may require partial exchange transfusion to lower serum hematocrit levels.
• Newborns with hydrops fetalis may require mechanical ventilation, thoracocentesis, pericardiocentesis, and paracentesis.

FOLLOW-UP

Section 7 of 10  

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

Complications

• Neurologic sequelae
• • Intrauterine demise of one twin can result in neurologic sequelae in the surviving twin.
  • Acute exsanguination of the surviving twin into the relaxed circulation of the deceased twin can result in intrauterine CNS ischemia.

Prognosis

Outcome is dependent upon gestational age at birth and whether intrauterine fetal brain ischemia occurred. The lower the gestational age at birth the greater the risk for long-standing neurologic or pulmonary sequelae. Catch-up growth occurs postnatally in most of the smaller donor twins.

MISCELLANEOUS

Section 8 of 10  

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

Medical/Legal Pitfalls

Monochorionic twin pregnancies are considered high-risk situations and require very close obstetrical monitoring. Newborns with twin-to-twin transfusion syndrome (TTTS) may be critically ill at birth and require specialized care in neonatal intensive care units. These infants are at significant risk for neurologic sequelae.

MULTIMEDIA

Section 9 of 10  

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

Media file 1:  Monozygotic twins with monochorionic, diamniotic placentation.
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Media type:  Image

Media file 2:  Monozygotic twins with monochorionic, monoamniotic placentation.
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Media type:  Image

REFERENCES

Section 10 of 10

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

1. Quintero RA, Morales WJ, Allen MH, Bornick PW, Johnson PK, Kruger M. Staging of twin-twin transfusion syndrome. J Perinatol. Dec 1999;19(8 Pt 1):550-5. [Medline].
2. Brackley KJ, Kilby MD. Twin-twin transfusion syndrome. Hosp Med. Jun 1999;60(6):419-24. [Medline].
3. Denbow ML, Battin MR, Cowan F, et al. Neonatal cranial ultrasonographic findings in preterm twins complicated bysevere fetofetal transfusion syndrome. Am J Obstet Gynecol. Mar 1998;178(3):479-83. [Medline].
4. Duncan KR. Twin-to-twin transfusion: update on management options and outcomes. Curr Opin Obstet Gynecol. Dec 2005;17(6):618-22. [Medline].
5. Elliot JP. Amniocentesis for twin-twin transfusion syndrome. Contemp Ob Gyn. 1992;37:30-47.
6. Fox C, Kilby MD, Khan KS. Contemporary treatments for twin-twin transfusion syndrome. Obstet Gynecol. Jun 2005;105(6):1469-77. [Medline].
7. Huber A, Diehl W, Bregenzer T, Hackelöer BJ, Hecher K. Stage-related outcome in twin-twin transfusion syndrome treated by fetoscopic laser coagulation. Obstet Gynecol. Aug 2006;108(2):333-7. [Medline].
8. Machin GA, Keith LG. Can twin-to-twin transfusion syndrome be explained, and how is it treated?. Clin Obstet Gynecol. Mar 1998;41(1):104-13. [Medline].
9. Milner R, Crombleholme TM. Troubles with twins: fetoscopic therapy. Semin Perinatol. Dec 1999;23(6):474-83. [Medline].
10. Sueters M, Middeldorp JM, Lopriore E, Oepkes D, Kanhai HH, Vandenbussche FP. Timely diagnosis of twin-to-twin transfusion syndrome in monochorionic twin pregnancies by biweekly sonography combined with patient instruction to report onset of symptoms. Ultrasound Obstet Gynecol. Oct 2006;28(5):659-64. [Medline].
11. Taylor MJ, Govender L, Jolly M, Wee L, Fisk NM. Validation of the Quintero staging system for twin-twin transfusion syndrome. Obstet Gynecol. Dec 2002;100(6):1257-65. [Medline].
12. Yamamoto M, Ville Y. Recent findings on laser treatment of twin-to-twin transfusion syndrome. Curr Opin Obstet Gynecol. Apr 2006;18(2):87-92. [Medline].

Article Last Updated: Aug 24, 2007