Twin-to-Twin Transfusion Syndrome – Facts

The cause of TTTS is attributed to unbalanced flow of blood through vascular channels that connect the circulatory systems of each twin via the common placenta. The shunting of blood through the vascular communications leads to a net flow of blood from one twin (the donor) to the other twin (the recipient). The donor twin develops oligohydramnios (low amniotic fluid) and poor fetal growth, while the recipient twin develops polyhydramnios (excess amniotic fluid), heart failure, and hydrops. If left untreated, the pregnancy may be lost due to lack of blood getting to the smaller twin, fluid overload and heart failure in the larger twin, and/or preterm (early) labor leading to miscarriage of the entire pregnancy.Some general treatment approaches consist of using laser energy to seal off the blood vessels that shunt blood between the fetuses. Because the surgical approach is via an operative fetoscope, there is minimal risk to the mother. Laser therapy for TTTS has been shown to provide improved pregnancy outcomes compared to alternative therapies. Although all treatment options should be discussed with your fetal surgeon.

Frequency

1 in 7 monochorionic pregnancies are afflicted with TTTS.

Diagnosis and Staging

The in utero diagnosis of TTTS is established by ultrasound. First, the presence of a shared placenta (monochorionic) confirmed. Ultrasounds performed earlier in the pregnancy may be useful in establishing the chorionicity (number of placentas). Ultrasound findings such as a single placenta, same fetal sex, and a “T-sign” in which the dividing membrane inserts perpendicular to the placenta are helpful in diagnosing a monochorionic twin gestation. TTTS is then diagnosed simply by assessing the discordance of amniotic fluid volume on either side of the dividing fetal membranes. The maximum vertical pocket (MVP) of amniotic fluid volume must be greater than or equal to 8.0 centimeters in the recipient’s sac, and less than or equal to 2.0 centimeters in the donor’s sac. Although TTTS is diagnosed via ultrasound, women with a monochorionic or monoamniotic pregnancy can be alerted to certain symptoms that may require medical attention. Symptoms may include a sudden increase in the size of the pregnant belly, a sudden increase in fatigue or pressure in the belly or back, and/or sudden unexplained increase in weight (eg. 7 lbs in a week or less). Once the diagnosis of TTTS is established, the severity of the condition may be assessed using the Quintero Staging System, as listed below. This staging system is based on the observations of several hundred patients with TTTS. Not only does this staging system mirror the progression of disease, but it has also been shown to be important in establishing the prognosis. An atypical presentation of TTTS may occur if the fetal bladder of the donor twin remains visible despite the presence of critically abnormal fetal Dopplers or hydrops. Quintero Staging System

• Stage I: The fetal bladder of the donor twin remains visible sonographically.
• Stage II: The bladder of the donor twin is collapsed and not visible by ultrasound.
• Stage III: Critically abnormal fetal Doppler studies noted. This may include absent or reversed end-diastolic velocity (flow) in the umbilical artery, absent or reverse flow in the ductus venosus (liver), or pulsatile flow in the umbilical vein.
• Stage IV: Fetal hydrops present.
• Stage V: Demise of either twin.

Management Options and Outcomes

Untreated, TTTS that presents before 28 weeks gestation is associated with approximately a 90% mortality rate. Because of the dismal prognosis of TTTS, various treatment methods have been advocated. Recent studies have shown improved outcomes in patients treated with laser therapy compared to the traditional method of serial amnioreductions (Quintero, AJOG, 2003; Senat, NEJM, 2004). In the European randomized trial, the study was interrupted prematurely because statistical improvement in pregnancy outcome in the laser therapy group was achieved at the time of an interval analysis (Senat, NEJM, 2004). Treatment Options

1. Laser Surgery: This surgical approach utilizes an operative fetoscope to deliver laser energy that then seals off the offending blood vessels on the surface of the common placenta. Because the vascular connections between the two fetuses are sealed, no further blood exchange between the fetuses takes place, thus eliminating the syndrome. Pregnancy outcomes after laser therapy for TTTS is as follows: approximately 85% of patients will have at least one fetus survive, 50% will have both survive, with a 5% risk of neurologic sequelae such as cerebral palsy. These results remain consistent regardless of Quintero Stage (i.e. severity).
2. Expectant Management: In this option the pregnancy would be followed with serial ultrasound examinations. There is approximately a 90% pregnancy loss rate in cases of TTTS diagnosed before 28 weeks gestation.
3. Amnioreduction: The purpose of this procedure is to remove excess amniotic fluid from the recipient’s sac in order to prevent premature birth or miscarriage. This procedure is done via a needle placed using ultrasound guidance. Because this approach does not treat the underlying cause of TTTS, amniotic fluid excess may recur, resulting in the need for multiple amnioreductions. Overall, the success rate of this treatment approach is approximately 66% chance of at least one fetal survivor, with an incidence of 15% chance of brain damage. Unlike laser therapy, the risk of fetal death and neurologic sequelae increases with increasing Quintero Stage.
4. Fetal Septostomy has been suggested as a treatment option for TTTS. This procedure entails the purposeful needling of the dividing membrane in the hopes to equalize the amniotic fluid within each sac. Studies have not shown improved outcomes using this approach. Moreover, the disruption of the dividing membrane may result in cord entanglement, which may be an additional cause of fetal death. Genearlly this procedure is not advised.
5. Umbilical Cord Occlusion: This procedure utilizes an operative fetoscope to interrupt the flow of blood through the umbilical cord of one of the fetuses. This fetus dies and remains inside the uterus for the duration of the pregnancy. The remaining twin will have an 85% chance of survival, and 5% risk of brain damage. Because the risks of this procedure are similar to laser therapy, but laser therapy provides the additional benefit of the chance of survival for both twins, this procedure is generally not offered for the treatment of TTTS unless the demise of one twin is a foregone conclusion due to fetal anomolies and condition.

Candidacy for Laser Surgery

To generally qualify for laser surgery, the following criteria usually must be met: Inclusion Criteria

1. Gestational age: 16 weeks 0 days to 26 weeks 0 days.
2. Diagnosis of TTTS:
   • Single (shared placenta) with thin dividing membrane (or no dividing membrane in the case of monoamniotic twins).
   • Polyhydramnios: maximum vertical pocket of 8 centimeters or more in the recipient twin, prior to amnioreduction.
   • Oligohydramnios: maximum vertical pocket of 2 centimeters or less in the donor twin, prior to amnioreduction.
   • Same gender, if visible.

General Exclusion Criteria

1. One or both babies have other major birth defects.
2. Genetic studies showing an uncompensated abnormality.
3. A hole in the dividing membrane that was intentionally made.
4. Ruptured fetal membranes (leakage of amniotic fluid from the vagina).
5. Chorioamnionitis (infection in the uterus).
6. Ultrasound evidence of brain damage of either fetus.
7. Placental abruption (separation of the placenta from the uterus).
8. Active labor.

Laser Surgery – Details of Procedure

Most surgeries are performed under local anesthesia with some intravenous sedation. A small incision (3 millimeters or about 1/10th of an inch) will be made and a trocar (small metal tube) will be inserted into the amniotic sac of the recipient twin. Amniotic fluid may be sent for genetic and microbiology studies. An endoscope (medical telescope) will be passed into the uterus. The blood vessels, which are visible on the surface of the placenta, will be analyzed, and all communicating vessels will be sealed off with laser energy. A second trocar may have to be inserted to complete the surgery, particularly if the placenta is anterior. At the conclusion of the surgery, the excess amniotic fluid may be drained from the sac of the recipient twin. You will be given antibiotics before and after surgery.

Laser Surgery – Postoperative Care

Typically, you will remain in the hospital for 1 to 2 days after surgery. You will then be sent home to the care of your primary obstetrician and perinatologist. Weekly ultrasound is recommended for the four weeks after surgery. Then, depending on the clinical circumstances, follow up ultrasounds generally should be performed every 2 – 3 weeks for the duration of the pregnancy (however it is the recommendation of Fetal Health to have weekly monitoring via ultrasound, NST’s, or other appropriate means.).

Additional Information (Nutrition)

If TTTS is diagnosed in its early stages some physicians will recommend a wait and see approach. Under this approach the mother is usually encouraged to consume increased amounts of protein, often through protein drinks like Boost or Ensure. Some physicians incorrectly indicate that TTTS can be “cured” by bed rest and proper nutrition (usually an increase in protein through protein drinks). Most studies indicate, regardless of a TTTS diagnosis, most pregnant women with multiples suffer malnutrition due to the nutritional needs of more than one fetus on the woman. Fetal Health does promote proper nutrition including increase in nutritious foods such as fruit, vegetables and an increase in protein via lean meats and/or protein supplements. Providing proper nutrition to the pregnant mother will only allow her to be stronger for the pregnancy and for her babies to have more than adequate nutrition for their growth.

Additional Resources

• UCSF Fetal Treatment Center – Informative Videos

The order that the treatment centers appear in, on this website, does not constitute a ranking or recommendation by the Fetal Health Foundation. Centers are listed in order of designated criteria such as years of experience, number of cases and/or other relevant criteria. Statistics are provided by the treatment centers themselves beginning in Q4 2009 and are updated periodically as new statistics are made available. The Fetal Health Foundation recommends patients consult with their own doctors as well as contacting a minimum of two treatment centers when choosing a center of care (when more than one is available). The Fetal Health Foundation, its members, staff, advisors and any other related parties are not responsible for the final medical decisions or outcomes as they relate to fetal treatment.

Twin-Twin Transfusion Syndrome (TTTS): TTTS occurs in approximately 10% of monochorionic twins.  This translates to approximately one in 3200 pregnancies.  Most researchers believe that TTTS develops in monochorionic twins from unbalanced sharing of blood through vascular communications in the common placenta.1, 2  A series of pathophysiologic changes ensues from the net shunting of blood from one twin (donor) to the other twin (recipient) resulting in donor fetus hypovolumia and oliguria, and recipient fetus volume overload and polyuria.  These hemodynamic derangements result in a cascade of events3, 4 that lead to donor twin oligohydramnios, recipient twin polyhydramnios, and characteristic anatomical and arterial/venous flow derangements that can be identified by ultrasound.5, 6*, 7  TTTS left untreated invariably culminates with perinatal death.8 The diagnosis of severe mid-trimester TTTS requires fulfillment of the following ultrasound-based criteria: (1) monochorionicity; (2) single maximal vertical pocket (MVP) of amniotic fluid ≤ 2.0 cm on one side of the dividing membranes, and an MVP of ≥ 8.0 cm on the other side.5  Once the diagnosis has been established, the syndrome may be staged according to the Quintero Staging System, as follows:  Stage I: meets criteria for TTTS without the ultrasound findings of the more advanced stages; Stage II: bladder of the donor twin not visible, normal Dopplers; Stage III: critically abnormal arterial or venous Doppler in either twin; Stage IV: hydrops fetalis; Stage V: demise of one or both twins.  The establishment of diagnostic criteria and classification of TTTS by Quintero et al 5 has allowed researchers to compare outcome data obtained from various therapeutic modalities as well as predict perinatal survival after treatment9*. The perinatal mortality rate of expectantly managed TTTS is as high as 95%.8  Of the various treatment approaches that have been considered for TTTS, the two that are currently considered the most viable are serial amniocentesis and selective laser photocoagulation of communicating vessels (SLPCV) via operative fetoscopy.  Serial amniocentesis (or amnioreduction) is a technically simple procedure that involves drainage of amniotic fluid from the polyhydramniotic recipient sac using vacuum-assisted devices attached to an 18-20 gauge spinal needle.  The volume of amniotic fluid that should be withdrawn has not been standardized, although usually the MVP in the recipient sac is brought down to approximately 6 cm or less.  Serial amniocentesis serves to significantly reduce the amount of amniotic fluid volume in the recipient sac, thereby diminishing overall uterine distention.  An international registry of TTTS patients treated by serial amniocentesis was published by Mari et al.10  Although it is unclear whether all 223 patients met criteria for TTTS based on today’s standards, the perinatal survival of at least one twin (one or two survivors) was 70.8%.  These results were similar to two controlled non-randomized trials that compared serial amniocentesis to laser therapy, which showed an at least one twin survival rate in the amnioreduction groups of 60.5%11 and 66.7%12.  However, this procedure should be regarded as a palliative one, for it serves to ameliorate only one symptom of TTTS, namely polyhydramnios, and does not treat the underlying disorder.  Because the offending vascular communications remain patent, the physiologic stress of the syndrome to the fetuses is allowed to persist throughout pregnancy.  This is evident clinically by the relatively high morbidity rates among neonatal survivors.  Data regarding long-term neurodevelopmental outcome in cases of TTTS managed with amnioreduction has recently emerged.  The rate of cerebral palsy ranged between 5.8% and 22.5%, while the rate of developmental delay (non-cerebral palsy) ranged from 7.5% to 28.6%.13-18 Unlike serial amniocentesis, SLPCV treats the primary pathogenic cause of TTTS by ablating all vascular communications.19  This surgery is performed using endoscopes of up to 3.3 mm in diameter which are used to directly visualize the vessels on the placental surface.  Once mapping of the vascular communications has been performed, those vessels are photocoagulated using laser energy that is delivered into the amniotic cavity by quartz fibers through the operating channel of the endoscope.  The surgical method of laser therapy has undergone several modifications.  The first attempts simply lasered all vessels that crossed the intertwin dividing membranes.20, 21  Recognizing that this approach would unnecessarily target innocent vessels that did not connect the circulatory systems of the twins and were not involved in the syndrome, Quintero et al developed the SLPCV technique.19  This technique selectively identifies only the vascular communications, which may in fact have absolutely no relationship to the location of the intertwin dividing membranes.  In two controlled non-randomized trials that used similar diagnostic approaches and compared serial amniocentesis to laser therapy using the SLPCV technique, the at least one twin survival rate in the laser therapy arms were 79%11 and 83.1%12.  Combining the data of these studies, the survival rate in the amnioreduction group was 64.4% (78/121) versus 81.5% (137/168) in the laser group (p=0.001).  The short-term neurological morbidity in these studies ranged between 4.2 and 5.6%. At a time when equipoise still existed between the potential benefits of the two treatment options for TTTS, the Eurofetus group conducted a randomized controlled trial that compared serial amniocentesis versus SLPCV.22  Pretrial power analysis projected the need for a total of 172 patients to show significant difference between the two treatment arms.  However, after enrollment of 142 patients, interim analysis revealed that the perinatal survival of at least one twin in the amnioreduction arm was 51% (36/70) versus 76% (55/72) in the laser therapy arm, which was statistically different (p=0.009), and the study was halted.  There was approximately a four-week difference in pregnancy duration (29 weeks vs. 33 weeks, p=0.003).  The amniocentesis group had significantly higher neurological complications (14% vs. 6%, p=0.02); this difference persisted at the six-month follow-up evaluation. Why do these studies that compare survival and neurological morbidity between amnioreduction and laser therapy show improved outcomes in the laser group?  The basic principle of SLPCV is that the offending vascular communications are ablated, thus providing treatment for the primary pathogenic cause of this syndrome.19  In properly performed laser surgeries, the pregnancy is converted to a functional dichorionic twin pregnancy, with perinatal outcomes approaching that of dichorionic twins.23** A recent randomized trial of amnioreduction versus laser therapy for TTTS was conducted in the United States.24*  The authors found no differences in perinatal outcome between the two groups (at least one twin survival 75% in the amnioreduction arm vs. 65% in the laser arm), but a significant difference in recipient survival for Quintero Stage III-IV patients with 63% survival in the amnioreduction arm versus 12.5% in the laser arm.  These results beg the question of why they are contrary to all prior studies comparing these two treatment modalities.  We have identified several flaws in the study design, the most important of which is the inconsistency regarding the inclusion criteria used in the trial.  Patients that did not meet criteria for TTTS (MVP < 8 cm in the recipient sac) were allowed to participate in the study.  This may explain the better than expected results in the amnioreduction arm.  Yet, why were the perinatal outcomes in the laser group lower than that reported in any other study?  The poorer than expected results in the laser arm may be related to the study design.  For example, all cases in this study underwent a prior amniocentesis prior to laser therapy.  This may lead to disruption of the membranes or placenta and result in technical difficulties during laser surgery.25*, 26  Another explanation for the relatively poor results in the laser arm of this study include the surgical techniques used in the study and/or surgeon inexperience, which may explain the 35% rate of maternal laparotomy in the laser arm24. Inclusion of non-TTTS patients, the study design used, and the surgical techniques employed make the results of this trial uninterpretable. A third generation laser technique has been reported recently.27**  This technique involves lasering the arteriovenous anastomoses from the donor to the recipient first, followed by the remaining communications.  By performing the laser ablation in this sequential fashion, the donor twin is kept from exsanguinating into the recipient twin intraoperatively.  This technique resulted in increased dual survival rate compared to standard SLPCV (74% vs. 57%, p=0.005).  The rate of at least one twin survivor was similar (91% vs. 88%).27 To summarize, current data supports laser therapy at an experienced center for first-line treatment of TTTS between 16 and 26 weeks gestation. References 1. Quintero R, Quintero L, Bornick P, Allen M, Johnson P. The donor-recipient (D-R) score: in vivo endoscopic evidence to support the hypothesis of a net transfer of blood from donor to recipient in twin-twin transfusion syndrome. Prenat Neonat Med 2000;5:84-91. 2. Bajoria R, Wigglesworth J, Fisk NM. Angioarchitecture of monochorionic placentas in relation to the twin- twin transfusion syndrome [see comments]. Am J Obstet Gynecol 1995;172(3):856-863. 3. Mahieu-Caputo D, Meulemans A, Martinovic J, Gubler MC, Delezoide AL, Muller F, Madelenat P, Fisk NM, Dommergues M. Paradoxic activation of the renin-angiotensin system in twin-twin transfusion syndrome: an explanation for cardiovascular disturbances in the recipient. Pediatr Res 2005;58(4):685-688. 4. Wieacker P, Wilhelm C, Prompeler H, Petersen KG, Schillinger H, Breckwoldt M. Pathophysiology of polyhydramnios in twin transfusion syndrome. Fetal Diagn Ther 1992;7(2):87-92. 5. Quintero R, Morales W, Allen M, Bornick P, Johnson P, Krueger M. Staging of twin-twin transfusion syndrome. J Perinatol 1999;19:550-555. 6. Chang YL, Chmait RH, Bornick PW, Allen MH, Quintero RA. The role of laser surgery in dissecting the etiology of absent or reverse end-diastolic velocity in the umbilical artery of the donor twin in twin-twin transfusion syndrome. Am J Obstet Gynecol 2006;195(2):478-483. *  This paper discusses role of the vascular communications versus placental share in the development of TTTS. 7. Ishii K, Chmait RH, Martinez JM, Nakata M, Quintero RA. Ultrasound assessment of venous blood flow before and after laser therapy: approach to understanding the pathophysiology of twin-twin transfusion syndrome. Ultrasound Obstet Gynecol 2004;24(2):164-168. 8. Saunders NJ, Snijders RJ, Nicolaides KH. Therapeutic amniocentesis in twin-twin transfusion syndrome appearing in the second trimester of pregnancy. Am J Obstet Gynecol 1992;166(3):820-824. 9. Kontopoulos EV, Quintero RA, Chmait RH, Bornick PW, Russell Z, Allen MH. Percent absent end-diastolic velocity in the umbilical artery waveform as a predictor of intrauterine fetal demise of the donor twin after selective laser photocoagulation of communicating vessels in twin-twin transfusion syndrome. Ultrasound Obstet Gynecol 2007;30(1):35-39. *  This paper quantifies the duration of absence of umbilical artery end-diastolic flow and correlates it with perinatal outcome in the donor fetus. 10. Mari G, Roberts A, Detti L, Kovanci E, Stefos T, Bahado-Singh RO, Deter RL, Fisk NM. Perinatal morbidity and mortality rates in severe twin-twin transfusion syndrome: results of the International Amnioreduction Registry. Am J Obstet Gynecol 2001;185(3):708-715. 11. Hecher K, Plath H, Bregenzer T, Hansmann M, Hackeloer BJ. Endoscopic laser surgery versus serial amniocenteses in the treatment of severe twin-twin transfusion syndrome. Am J Obstet Gynecol 1999;180(3 Pt 1):717-724. 12. Quintero RA, Dickinson JE, Morales WJ, Bornick PW, Bermudez C, Cincotta R, Chan FY, Allen MH. Stage-based treatment of twin-twin transfusion syndrome. Am J Obstet Gynecol 2003;188(5):1333-1340. 13. Cincotta RB, Gray PH, Phythian G, Rogers YM, Chan FY. Long term outcome of twin-twin transfusion syndrome. Arch Dis Child Fetal Neonatal Ed 2000;83(3):F171-176. 14. Mari G, Detti L, Oz U, Abuhamad AZ. Long-term outcome in twin-twin transfusion syndrome treated with serial aggressive amnioreduction. Am J Obstet Gynecol 2000;183(1):211-217. 15. Haverkamp F, Lex C, Hanisch C, Fahnenstich H, Zerres K. Neurodevelopmental risks in twin-to-twin transfusion syndrome: preliminary findings. Eur J Paediatr Neurol 2001;5(1):21-27. 16. Frusca T, Soregaroli M, Fichera A, Taddei F, Villani P, Accorsi P, Martelli P. Pregnancies complicated by Twin-Twin transfusion syndrome: outcome and long-term neurological follow-up. Eur J Obstet Gynecol Reprod Biol 2003;107(2):145-150. 17. Lopriore E, Nagel HT, Vandenbussche FP, Walther FJ. Long-term neurodevelopmental outcome in twin-to-twin transfusion syndrome. Am J Obstet Gynecol 2003;189(5):1314-1319. 18. Dickinson JE, Duncombe GJ, Evans SF, French NP, Hagan R. The long term neurologic outcome of children from pregnancies complicated by twin-to-twin transfusion syndrome. Bjog 2005;112(1):63-68. 19. Quintero R, Morales W, Mendoza G, Allen M, Kalter C, Giannina G, Angel J. Selective photocoagulation of placental vessels in twin-twin transfusion syndrome: Evolution of a surgical technique. Obstet Gynecol Surv 1998;53(12):s97-s103. 20. De Lia JE, Kuhlmann RS, Harstad TW, Cruikshank DP. Fetoscopic laser ablation of placental vessels in severe previable twin-twin transfusion syndrome. Am J Obstet Gynecol 1995;172(4 Pt 1):1202-1208; discussion 1208-1211. 21. Ville Y, Hyett J, Hecher K, Nicolaides K. Preliminary experience with endoscopic laser surgery for severe twin-twin transfusion syndrome. N Engl J Med 1995;332:224-227. 22. Senat MV, Deprest J, Boulvain M, Paupe A, Winer N, Ville Y. Endoscopic laser surgery versus serial amnioreduction for severe twin-to-twin transfusion syndrome. N Engl J Med 2004;351(2):136-144. 23. Lenclen R, Paupe A, Ciarlo G, Couderc S, Castela F, Ortqvist L, Ville Y. Neonatal outcome in preterm monochorionic twins with twin-to-twin transfusion syndrome after intrauterine treatment with amnioreduction or fetoscopic laser surgery: comparison with dichorionic twins. Am J Obstet Gynecol 2007;196(5):450 e451-457. ** This paper reports similar perinatal outcome of successfully laser treated TTTS pregnancies as compared to dichorionic twins.  This supports the concept that laser therapy converts the pregnancy to a functional dichorionic twin gestation via ablation of all vascular communications. 24. Crombleholme TM, Shera D, Lee H, Johnson M, D’Alton M, Porter F, Chyu J, Silver R, Abuhamad A, Saade G, Shields L, Kauffman D, Stone J, Albanese CT, Bahado-Singh R, Ball RH, Bilaniuk L, Coleman B, Farmer D, Feldstein V, Harrison MR, Hedrick H, Livingston J, Lorenz RP, Miller DA, Norton ME, Polzin WJ, Robinson JN, Rychik J, Sandberg PL, Seri I, Simon E, Simpson LL, Yedigarova L, Wilson RD, Young B. A prospective, randomized, multicenter trial of amnioreduction vs selective fetoscopic laser photocoagulation for the treatment of severe twin-twin transfusion syndrome. Am J Obstet Gynecol 2007;197(4):396 e391-399. *  This is the first report that showed significantly worse outcome in the TTTS pregnancies treated by laser therapy versus amnioreduction in regards to recipient survival in Quintero Stage III/IV TTTS.  Overall perinatal outcomes between the two groups were similar.  Due to several concerns regarding study design, surgical techniques, and surgeon experience, the results of this trial should be summarily questioned. 25. Chmait RH, Rossi AC, Quintero RA. Paradoxical scalloped placenta with polyhydramnios in twin-twin transfusion syndrome. J Matern Fetal Neonatal Med 2007;20(1):29-32. *  Amnioreduction prior to laser therapy for TTTS may result in a scalloped placenta, as reported in this paper. 26. Quintero RA, Kontopoulos EV, Chmait R, Bornick PW, Allen M. Management of twin-twin transfusion syndrome in pregnancies with iatrogenic detachment of membranes following therapeutic amniocentesis and the role of interim amniopatch. Ultrasound Obstet Gynecol 2005;26(6):628-633. 27. Quintero RA, Ishii K, Chmait RH, Bornick PW, Allen MH, Kontopoulos EV. Sequential selective laser photocoagulation of communicating vessels in twin-twin transfusion syndrome. J Matern Fetal Neonatal Med 2007;20(10):763-768. ** By occluding the vascular communications in a specific order, the intraoperative hemodynamic conditions for the fetuses afflicted with TTTS can be optimized.  This technique resulted in improved dual survival rate.