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Twin-to-twin transfusion syndrome (TTTS)

Twin-to-twin transfusion syndrome (TTTS). 報告 : 黃貞瑜 醫師 指導 : 洪正修主任、楊明智主任. > 20% discordance in birthweight, and > 5 g/dL discordance in cord haemoglobin levels –insufficient

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Twin-to-twin transfusion syndrome (TTTS)

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  1. Twin-to-twin transfusion syndrome (TTTS) 報告: 黃貞瑜 醫師 指導: 洪正修主任、楊明智主任

  2. > 20% discordance in birthweight, and > 5 g/dL discordance in cord haemoglobin levels –insufficient • ultrasound-based criteria, with particular attention to amniotic fluid discordance, bladder volumes, and fetal Doppler studies.

  3. Pathophysiology1. Placental architecture • Almost all monochorionic twins have intertwin vascular anastomoses. • Arterio-arterial (AA) anastomoses and veno-venous (VV) anastomoses are superficial anastomoses, travelling across the surface of the placenta without interruption between the two cord insertions.

  4. Arterio-venous (AV) anastomoses are deep anastomoses, where an unpaired artery and vein pierce the chorionic plate in close adjacency to supply a shared placental cotyledon. --provide unidirectional flow of blood from the donor to the recipient. • TTTS results from intertwin transfusion across shared placental vascular anastomoses • TTTS occurred uncommonly (15%) despite the high frequency of occurrence of cross-placental vascular communication.

  5. TTTS is more likely to develop when there is a paucity of bi-directional AAs and VV anastomoses that can assist with regulation of intertwin circulatory imbalances. • The larger the number and type of intertwin anastomoses, the less frequently clinical TTTS is observed. • the antenatal detection of AA anastomoses predicts higher perinatal survival in pregnancies complicated by TTTS.

  6. Pathophysiology2. The fetal response • Transfusion through the unidirectional AV anastomoses creates hydrostatic differences between the twins. • Atrial natriuretic peptide (ANP) and vasopressin levels in the twins diverge; the donor responds with oliguria, and the recipient with polyuria and polyhydramnios (Quintero stage 1).

  7. The resultant haemoconcentration in the recipient creates an osmotic gradient from the maternal compartment, worsening the polyhydramnios • As donor perfusion pressure continues to fall urine production finally ceases (Quintero stage 2), resulting in a ‘stuck twin’.

  8. The resultant inability to swallow aggravates the donor twin's hypotension, and vasoconstrictor peptides, such as the renin-angiotensin system (RAS) mediators, increase dramatically increased arterial resistance in the donor's placental territory growth restriction. • Absent or reversed end-diastolic flow (A/REDF) in the donor umbilical artery (UA) may be seen (Quintero stage 3: donor).

  9. These RAS mediators are also transfused to the recipient via placental anastomoses（ similar cord levels of renin and aldosterone despite discordant renal expression of renin between donors and recipients. ） • Systemic hypertension in the recipient fetus, initiated by the increase in cardiac output, now worsens. • [endothelin and fetal natriuretic peptides]: higher in recipient twins--these mediators likely work synergistically to induce pressure-overload cardiomyopathy.

  10. Fetal echocardiography in recipient ：the presence of cardiomegaly secondary to biventricular hypertrophy, with the majority exhibiting right ventricular systolic and biventricular diastolic dysfunction. • Right ventricular outflow tract obstruction may evolve （10% of recipient fetuses ） • Venous Dopplers – ductus venosus (DV) and umbilical vein (UV) – may now deteriorate (Quintero stage 3: recipient).

  11. Continuing feto–fetal transfusion in the face of such cardiac dysfunction  progression to fetal hydrops (Quintero stage 4). • Whether by terminal hypoperfusion in the donor, or by cardiac failure in the recipient, single fetal demise may ensue (Quintero stage 5). • At or around the time of this death, acute feto–fetal haemorrhage from the survivor into the placental and fetal vascular compartment of the dead twin can occur through the patent intertwin vascular anastomoses.  profound hypotension  high risk of death or severe neurological injury (approximately 30% for each) in the co-twin.

  12. Disease staging

  13. Screening for TTTS1. nuchal translucency • Discordant crown–rump length in the first trimester does not identify those pregnancies destined to develop TTTS, but increased nuchal translucency (NT) and/or NT discordance in monochorionic twins is associated with an increased risk for subsequent development of TTTS. • Increased NT (> 95th centile) at 10–14 weeks a/w a likelihood ratio of 3.5 (95% CI, 1.9–6.2) for the development of severe TTTS. （Sebire et al. Hum Reprod 2000 ）

  14. This transient finding probably reflects impaired ventricular function of the immature fetal heart in the hypervolaemic recipient twin; • the improvement with advancing gestation is likely because of improved ventricular compliance and the establishment of diuresis.

  15. Screening for TTTS2. First trimester ductus venosus (DV) • Among twin with discordant NT, discordant reversal of the ‘a’ wave in the DV was useful in identifying those twins that went on to develop TTTS. （Matias et al. J Matern Fetal Med 2005 ）

  16. Screening for TTTS3. Intertwin membrane folding • an early ultrasound marker of amniotic fluid discordance • the likelihood ratio of membrane folding on ultrasound at between 15 and 17 weeks gestation for the subsequent development of TTTS was 4.2 (95% CI 3.0–6.0). （Sebire et al. Hum Reprod 2000 ）

  17. Surveillance for TTTS • BIW after NT assessment for monochorionic twins • amniotic fluid discordance, intertwin membrane folding, bladder volumes, and Doppler studies.

  18. Diagnosis and assessment of TTTS • Minimum sonographic criteria ： (i) monochorionic twins, that is, single placenta, same sex twins, and absence of intervening chorion (‘twin peak’ sign); (ii) oligohydramnios (maximal vertical pocket (MVP) ≤ 2 cm) in the donor sac; and (iii) polyhydramnios (MVP ≥ 8 cm) in the recipient sac.

  19. Differential diagnoses • selective intrauterine growth restriction (IUGR), which also affects 15% of monochorionic twins, and may result in oligohydramnios, delayed growth and abnormal umbilical Dopplers in one twin. • monochorionic twins discordant for anomaly (particularly renal agenesis) may result in anhydramnios around one twin. -- neither of these conditions is associated with polyhydramnios in the other twin

  20. Treatment options • untreated perinatal mortality for severe midtrimester TTTS is up to 90%. • Selective laser photocoagulation (SLPC) of intertwin vascular anastomoses • Amnioreduction and septostomy • cord occlusion in TTTS

  21. TTTS in monochorionic monoamniotic (MCMA) • much less common ∵nearly all MCMA placentas have AA anastomoses, and a decreased number of AV anastomoses, when compared to MCDA placentas. • may still occur --will lack the classic sign of discordant sac size. --The combination of polyhydramnios in the single amniotic cavity with discordant bladder size is usually sufficient to make the diagnosis, particularly where there are discordant cord diameters and abnormal Doppler waveforms. -- Stage 1 disease, however, may escape detection.

  22. TTTS in Dichorionic diamnion? Dizygotic twins?

  23. 1. monochorionic dizygotic twins seems increase after pregnancy by ART(?) • Monochorionic (MC) dizygotic twins (DZT) are extremely rare in natural pregnancy • Unusual monochorionic placentation with heterosexual twins. （ ObstetGynecol 1970;36:621-5. ） • sex-discordant monochorionic twins conceived by in vitro fertilization （The New England Journal of Medicine. 2003. 349(2): 154-159 ） • DZ monochorionic twins conceived by ART, of which one has both Klinefelter syndrome and Beckwith-Wiedemann syndrome (BWS). （Journal of Pediatrics.2005, 146(4):565-567） --J Hum Genet. 2005;50(1):1-6.

  24. 2. Twins with two separate placental masses can still be monochorionic and therefore have vascular anastomoses pathogenesis of bipartite placentation in MC twinning ：not clear American Journal of Obstetrics and Gynecology 2006

  25. True DADC? • The combination of the lambda sign or 2 separate placentas on sono in twin pregnancies predicts dichorionicity with a sensitivity of 97% and a specificity of 100% ; “T” sign -- the most useful sign in predicting monochorionicity with a sensitivity of 100% and a specificity of 98%. （ GA 10-14 wks） • 2 separate placental masses are not per se DC • Microscopic examination of the intertwin membrane after delivery -- the gold standard for chorionicity

  26. If true DADC • Anastomotic communication was found almost universally in monochorionic placentation and very rarely with dichorionic placentas. （Placental injection studies in twin gestation. Robertson EG. Am J Obstet Gynecol 1983; 147(2): 170-174 ） • Vascular Anastomoses in Dichorionic Diamniotic-Fused Placentas：side-to-side connections between small subchorionic vessels. （International Journal of Gynecological Pathology. 22(4):359-361, October 2003 ）

  27. Non-immune hydrops fetalis • Cardiac failure • Anemia • Arteriovenous shunts • Mediastinal compression • Metabolic disorder • Fetal infection/tumor • Congenital renal/pulmonary/GI/skeletal defect • Chromosomal anomalies

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