Twin-twin transfusion syndrome: etiology, severity and rational management

Relationship Between the Types and Diameters of Residual Vessels and Secondary TAPS after Fetoscopic Laser Surgery for TTTS

Objective This study aimed to investigate the relationship between the characteristics and diameters of residual anastomoses and the occurrence of twin anemia-polycythemia sequence (TAPS) in twin-to-twin transfusion syndrome (TTTS) patients with placental vascular injection after fetoscopic laser surgery (FLS).

Methods A total of 90 cases of pregnant women who underwent FLS owing to TTTS were collected in the university hospital from May 2018 to December 2020. Therein, 40 cases received placental injection and were divided into the TAPS group and non-TAPS group according to the postoperative complications. The number of residual superficial anastomoses was counted and the diameter was measured.

Results Among the placentae of nine patients in the TAPS group, two cases had no superficial anastomoses, and seven cases had 16 superficial anastomoses, including eight arterio-venous (AV) anastomoses, two veno-arterial (VA) anastomoses, three arterio-arterial (AA) anastomoses and three veno-venous (VV) anastomoses. Among the placentae of 31 patients in the non-TAPS group, 19 cases had no superficial anastomoses, and 12 cases had 18 superficial anastomoses, including two AV anastomoses, five VA anastomoses, seven AA anastomoses, and four VV anastomoses; and both the two cases of AV anastomoses were accompanied by AA anastomoses. The number of AV anastomoses in the placentae of the TAPS group was significantly elevated compared with that in the non-TAPS group (p<0.05). While there was no significant difference in the numbers of placentae with superficial anastomoses, the numbers of blood vessels with VA anastomoses, VV anastomoses, and AA anastomoses between the two groups (p>0.05). Through analyzing the diameters of 34 superficial anastomoses in the two groups, it was shown that the diameters of AA anastomoses in the non-TAPS group were significantly larger than those in the TAPS group (Z=1.97, p<0.05). There was no statistical difference in the diameters of AV anastomoses (Z=0.52, p>0.05), VA anastomoses (Z=0.98, p>0.05), and VV anastomoses (Z=0.36, p>0.05). The differences of the birth weight and inter-twin hemoglobin difference were statistically significant (p<0.05). The result indicated that the differences between age, gestational weeks at operation, delivery, and mean operating times were not statistically significant (p>0.05).

Conclusion The increase in the number of AV anastomoses could obviously elevate the incidence of TAPS. The probability of TAPS occurrence is reduced following the increased diameters of AA anastomoses, demonstrating that AA anastomosis has a protective effect on TTTS patients.

Flexible fetoscope in the treatment of twin-to-twin transfusion syndrome

BACKGROUND

Twin-to-twin transfusion syndrome (TTTS) could be treated with fetoscopic laser photocoagulation. For patients with placenta located on the anterior wall of uterus, surgical procedures are difficult. To solve this problem, a flexible fetoscope was designed in our department.

METHODS

The flexible fetoscope was made up of polyurethane, fiberglass and stainless steel coils. The specular body was soft and could bend encountering obstacles, which reduced the possibility of injury to the fetus and placenta. The distal tip of the body could curve from -180° to +270° with the control of the handweel. Three pregnant women of TTTS with anterior placenta was operated with this instrument.

RESULT

All pregnant women were treated smoothly and gave live twins birth at term. Through angiography, it was demonstrated that the vascular connections on the surface had been coagulated.

CONCLUSION

The flexible fetoscope was a novel instrument in treating TTTS, especially for the anterior placenta.

Neonatal outcomes between discordant monochorionic and dichorionic twins

OBJECTIVES

This study aimed to compare obstetrical complications and neonatal outcomes between monochorionic and dichorionic discordant twin pregnancies.

STUDY DESIGN

We enrolled 296 patients with twin pregnancy who delivered at Busan Paik Hospital between January 2014 and December 2017. The prevalence of obstetrical complications, neonatal mortality between monochorionic and dichorionic twins was compared. We also investigated whether there is a difference in neonatal outcome and neonatal morbidity between monochorionic discordant twins without monochorionic-specific complications and dichorionic discordant twins.

RESULTS

The risk of fetal death in utero (13.2 versus 5.2%, p = .025) and inter twin birth weight discordance (35.1 versus 20.8%, p = .031) is increased in monochorionic twins than in dichorionic twins. However, no difference was noted in obstetrical complication and neonatal mortality and morbidity between two groups. Among twin pregnancies with intertwin birth weight discordance, after excluding fetal death in utero and monochorionic specific complication, there was no difference in obstetrical complication and neonatal mortality and morbidity according to chorionicity. There was no difference in neonatal morbidity between monochorionic twins and dichorionic twins when comparing larger neonates and smaller neonates of each group.

CONCLUSIONS

Risk of birth weight discordance is higher in monochorionic twin but no significant difference was observed in maternal outcomes, neonatal mortality and morbidity between noncomplicated monochorionic and dichorionic discordant twins.

Developmental and behavioral outcomes of uncomplicated monochorionic diamniotic twins born in the third trimester

BACKGROUND

Relatively little is known about the neurodevelopmental and behavioral outcomes of monochorionic diamniotic (MCDA) twin pregnancies where there are no antenatal complications peculiar to monochorionicity or prematurity.

METHODS

Twenty-two MCDA twins (44 children) with an average age of 4.3 years, and with no antenatal complications detected by 28 weeks of gestation, were recruited from a feto-maternal unit database. Parents completed a battery of neurodevelopmental and behavioral assessment questionnaires.

RESULTS

Eighteen children (41%) were identified as having developmental or behavioral concerns, predominantly of mild severity, which in turn were associated with a lower birth weight of medium effect size (Cohen's d=0.59).

CONCLUSION

MCDA twins delivered in the third trimester with no antenatal monochorionic complications in the first two trimesters appear to be at risk for subtle neurodevelopmental difficulties, associated with a lower birth weight. Ongoing developmental surveillance of these children during preschool-age is indicated for early identification and intervention.

What-and why-the pathologist should know about twin-to-twin transfusion syndrome

Approximately 20% of all twin pregnancies are monochorionic. Between 9% and 15% of all monochorionic twin gestations are complicated by severe chronic twin-to-twin transfusion syndrome (TTTS), characterized by a gradual shift of blood volume from the donor twin to the recipient twin through placental vascular connections [1 - 3] . The prognosis of severe, untreated chronic TTTS diagnosed in midtrimester fetuses is extremely poor, with mortality rates exceeding 70% [4] . Since publication of the results of the Eurofoetus trial in 2004, laser photocoagulation of the intertwin anastomoses has become accepted as the optimal first-line therapy for severe TTTS diagnosed before 26 weeks of gestation. While laser treatment of vascular communications was initially limited to selected fetal treatment centers, its increasingly widespread use has resulted in the exposure of more pathologists, even in less specialized institutions, to laser-treated placentas. Furthermore, the surge in laser coagulation has revived the general medical, scientific, and public interest in the placental and choriovascular findings in monochorionic twin placentas. The pathologist's understanding of the pathophysiology of TTTS and of TTTS-associated placental pathology, including the findings related to laser ablation of the anastomoses, can be of great benefit to the involved obstetric/neonatal/surgical team and, ultimately, to the patients. In this review, we summarize the current knowledge of the placental contributions to TTTS and other complications of monochorionic twinning and describe the strengths and limitations of placental examination in these settings. It is our expectation that overviews such as this may serve as a template to generate consensus guidelines for standardized and evidence-based pathologic evaluation of monochorionic twin placentas.

Treatment of twin-twin transfusion syndrome with proximate umbilical cord insertions

Laser ablation of anastomosis is one method for treatment of twin-twin transfusion syndrome in monochorionic pregnancies. Sonographic mapping of the umbilical cord insertions is an important aspect of the preoperative workup before laser ablation. Proximate umbilical cord insertions can be potential contraindications to laser ablation. This series discusses 6 such cases.

Specific complications of monochorionic twin pregnancies: twin-twin transfusion syndrome and twin reversed arterial perfusion sequence

Monochorionic twins are subjected to specific complications which originate in either imbalance or abnormality of the single placenta serving two twins. This unequal placental sharing can cause complications including twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS), selective intrauterine growth restriction or twin reversed arterial perfusion sequence (TRAP). Monochorionicity also makes the management of these specific complications as well as that of a severe malformation in one twin hazardous since the spontaneous death of one twin exposes the co-twin to a risk of exsanguination into the dead twin and its placenta. The latter is responsible for the death of the co-twin in up to 20% of the cases and in ischemic sequelae in about the same proportions in the survivors. Although the symptoms of all these complications are very different, the keystone of their management comes down to either surgical destruction of the inter-twin anastomoses on the chorionic plate when aiming at dual survival or selective and permanent occlusion of the cord of a severely affected twin aiming at protecting the normal co-twin. This can be best achieved by fetoscopic selective laser coagulation and bipolar forceps cord coagulation respectively.

Short- and long-term outcome in stage 1 twin-to-twin transfusion syndrome treated with laser surgery compared with conservative management

OBJECTIVE

We sought to compare short- and long-term outcome in Quintero stage 1 twin-to-twin transfusion syndrome (TTTS), managed with laser surgery or conservatively.

STUDY DESIGN

We conducted a retrospective study of all monochorionic twin pregnancies with stage 1 TTTS referred to our center. Primary outcomes were perinatal survival, neonatal morbidity, and long-term neurodevelopmental outcome.

RESULTS

Fifty women presented with stage 1 TTTS of which 40% (20/50) was treated with laser and 60% (30/50) was managed conservatively. Perinatal survival of both or at least 1 twin was 65% (13/20) and 85% (17/20) in the laser group, and 77% (23/30) and 97% (29/30) in the conservatively managed group (P = .52 and P = .29), respectively. Long-term neurodevelopmental impairment of the surviving infants was found in 0% (0/21) vs 23% (7/30), respectively (P = .03).

CONCLUSION

In this retrospective study, long-term outcome in stage 1 TTTS was better after laser surgery than with conservative management, suggesting the need for a randomized controlled trial.

Residual anastomoses in twin-to-twin transfusion syndrome treated with selective fetoscopic laser surgery: localization, size, and consequences

OBJECTIVE

To study the localization and size of residual anastomoses in twin-to-twin transfusion syndrome treated with fetoscopic laser surgery and correlate the findings with outcome.

STUDY DESIGN

Placental injection in twin-to-twin transfusion syndrome placentas treated with laser was performed by using colored dye.

RESULTS

A total of 77 twin-to-twin transfusion syndrome placentas were included in the study. Residual anastomoses (n = 48) were found in 32% (25/77) of lasered placentas. Most residual anastomoses were localized near the margin of the placenta. The majority of residual anastomoses (67%; 32/48) were very small (diameter, < 1 mm). Eleven of the 25 cases (44%) in the residual anastomoses group developed twin anemia-polycythemia sequence.

CONCLUSION

Most residual anastomoses in twin-to-twin transfusion syndrome placentas treated with laser are very small and localized near the placental margin. Almost half of cases with residual anastomoses developed twin anemia-polycythemia sequence after laser surgery.

A case of successful selective abortion using radio-frequency ablation in twin pregnancy suffering from severe twin to twin transfusion syndrome

Twin to twin transfusion syndrome (TTTS) is one of the major complication of monochorionic twin pregnancy which is mainly understood by placental vascular anastomosis. Perinatal mortality and morbidity is high as 80-100% if untreated and even higher if the disease is developed at early stage. Variety of methods of isolating or intercepting placental vascular anastomosis are introduced, but they are only available in centers where all the required equipments are prepared. We report here a case of TTTS complicated with severe polyhydroamnios during the second trimester. The blood supply to donor twin was interrupted successfully at 19(+2) weeks of gestation by minimally invasive radio-frequency cord ablation, under ultrasound guidance. The normal recipient twin was delivered successfully at 35 weeks of gestation and had no eventful neonatal course.

Endoscopic laser surgery in severe second-trimester twin-twin transfusion syndrome: a three-year experience from a Latin American center

OBJECTIVE

In order to assess the outcome of pregnancies complicated by severe second trimester twin-twin transfusion syndrome (TTTS) undergoing treatment with endoscopic laser surgery, we reviewed our experience following the implementation of an institutional fetal surgery program.

METHODS

Patients presenting with monochorionic-diamniotic twin pregnancies complicated by severe TTTS before 26 weeks of gestation were offered endoscopic laser surgery to coagulate placental vascular anastomoses. Using regional anesthesia and guided by real-time sonography, anastomoses were identified and selectively coagulated. At the end of the procedure, amniodrainage was performed to restore normal amniotic fluid volume. Follow-up and delivery were carried out at the referring institutions. Six-month follow-up was performed in all cases.

RESULTS

During a 3-year period from September 2003 to December 2006, 33 consecutive cases of severe TTTS were operated on at a median gestational age of 21 weeks (range 17-25). Nine (27.3%) cases were classified as stage II, 21 (63.6%) as stage III, and three (9.1%) as stage IV. The placenta was anterior or predominantly anterior in 15 (45.5%) of the cases. Overall, both twins were born alive in 16 (48.5%) cases, only one twin was born alive in 11 (33.3%), and neither was born alive in the remaining six (18.2%). Therefore, 81.8% (27 of 33) of the pregnancies resulted in at least one liveborn infant. Among them, the mean gestational age at delivery was 32 weeks (range 23-38) and the mean birthweight of the liveborn infants was 1591 g (range 350-3800). Thirty-four infants survived the perinatal period, yielding an overall perinatal survival rate of 51.5%, with 75.8% (25 of 33) of the pregnancies resulting in at least one perinatal survivor. All neonatal deaths were associated with extreme prematurity.

CONCLUSIONS

This preliminary experience suggests that selective laser coagulation appears to be a good treatment option in cases of monochorionic twin pregnancies complicated by severe TTTS. However, technical skills and adequate equipment are required for implementing a fetal surgery program. Auditing outcomes during the learning curve would help in identifying potential problems.

A definition of selectivity in laser coagulation of chorionic plate anastomoses in twin-to-twin transfusion syndrome and its relationship to perinatal outcome

OBJECTIVE

This study was undertaken to correlate selectivity of surgery and perinatal outcome in twin-to-twin transfusion syndrome treated by endoscopic laser coagulation, using a quantitative definition of selectivity.

STUDY DESIGN

287 consecutive cases of severe twin-to-twin transfusion syndrome were reviewed. A selectivity index was built as the ratio of selective over nonselective coagulations per procedure. Outcome measures were survival at 28 days and failure of surgery as defined by recurrence of twin-to-twin transfusion syndrome or fetofetal hemorrhage.

RESULTS

Two populations were identified: a high selectivity group (63.8%) and a low selectivity group (36.2%). Survival of at least one twin and survival of both twins were higher in the high-selectivity group (p = .007 and p = .04 respectively). Failure of surgery rates were similar in both groups.

CONCLUSION

A quantitative definition of selectivity appears justified by the large variations found in the practice of a single center and by significant differences in outcome. Survival is significantly improved in highly selective procedures.

Stage I twin-twin transfusion syndrome: rates of progression and regression in relation to outcome

OBJECTIVES

Twin-twin transfusion syndrome (TTTS) results in high rates of perinatal mortality and neurological morbidity. Fetoscopic laser ablation of placental anastomoses is now established as the treatment of choice for advanced disease. However, there remains controversy about its use in early-stage TTTS, in which laser-related fetal losses need to be balanced against relatively favorable outcomes with more conservative approaches. We investigated rates of progression and regression in Stage I TTTS and determined factors influencing the course of the disease.

METHODS

We undertook a retrospective observational study of all TTTS cases referred to our tertiary referral fetal medicine service from 2000 to 2006. In patients presenting with Stage I TTTS, the following variables were evaluated for their ability to predict the course and progression of the disease: gestational age (GA) at presentation, amniotic fluid index, recipient and donor deepest vertical pool, presence of artery-artery anastomoses, small-sized bladder compared to normal donor bladder and fetal size discordance. Study end-points were disease regression or progression, and neonatal survival at 28 days.

RESULTS

Among 132 consecutive cases of TTTS, 46 women presented with Stage I disease. In the majority (69.6%), disease remained stable (28.3%) or regressed (41.3%). Of cases that progressed, 79% did so within 2 weeks and 93% progressed to at least Stage III. No factor was significantly linked with progression or regression, although there was a trend towards the absence of an artery-artery anastomosis (P = 0.10) and the presence of a small rather than normal donor bladder (P = 0.10) influencing progression, and later GA at presentation (P = 0.07) influencing regression. At least one infant survived in 83% of cases and there was double survival in 59%. Perinatal outcome was significantly better in cases that regressed (the rates of at least one survivor and double survival being 89% and 89%, respectively) or remained Stage I (77% and 61%, respectively), compared with those cases that progressed (79% and 14%, respectively). Treatment with amnioreduction at first presentation did not influence progression or regression.

CONCLUSIONS

This study demonstrates that a high percentage of Stage I TTTS cases regress or remain early stage. Identification of factors predicting progression would facilitate the selection of patients for definitive therapy, while avoiding treatment-related morbidities in mild or transient disease.

Laparoscopically Guided Uterine Entry for Fetoscopy in Twin-to-Twin Transfusion Syndrome with Completely Anterior Placenta: A Novel Technique

OBJECTIVE

Laser coagulation of anastomotic vessels on the placental surface is the treatment of choice in severe second trimester twin-to-twin transfusion syndrome (TTTS). This procedure is associated with technical difficulties when the placenta is located on the anterior side of the uterus. We describe a novel technique for fetoscopy in TTTS with completely anterior placenta where laparoscopy is used to guide safe percutaneous insertion of the fetoscope through the lateral abdominal wall and the dorsal side of the uterus.

METHODS

Prospective controlled series of 16 TTTS pregnancies with completely anterior placenta (study group) treated with this novel technique. Studied outcomes were technical result of the procedure and perinatal survival. Outcome in the study group was compared with outcome of 49 TTTS pregnancies treated with conventional percutaneous fetoscopic laser without laparoscopy, 9 of these with partially anterior placenta (control group A) and 40 with lateral or posterior placenta (control group B).

RESULTS

In the study group, the procedure-related complication rate was 25% (4/16). In 1 case, uterine entry of the fetoscope from the lateral abdominal wall was not possible due to complex bowel adhesions. In 3 patients, intra-amniotic haemorrhage occurred after fetoscopic entry, preventing complete laser coagulation of anastomoses. One of these patients required 2 units of blood transfusion. The procedure-related complication rate in control groups A and B was 22% (2/9) and 5% (2/40), respectively (intra-amniotic haemorrhage n = 3, severe leakage of amniotic fluid into the peritoneal cavity, n = 1). Perinatal survival in the study group, control group A and control group B was 63% (20/32), 78% (14/18) and 70% (56/80), respectively.

CONCLUSION

Combined laparoscopy and fetoscopy is a novel technique that enables safe uterine entry and creates optimal visualisation for laser coagulation of inter-twin anastomoses in TTTS pregnancies with completely anterior placenta. The procedure-related complication rate and perinatal survival rate were similar compared to the conventional percutaneous technique. Procedure-related complications occur more often with partially or completely anterior placenta.

Modeling Severely Discordant Hematocrits and Normal Amniotic Fluids After Incomplete Laser Therapy in Twin-To-Twin Transfusion Syndrome

Our objective was to explain the clinical presentations of sustained arteriovenous anastomotic transfusion of blood after incomplete laser therapy in twin-to-twin transfusion syndrome (TTTS). We extended our mathematical model of TTTS by adding the dynamics of hematocrit, and simulated incomplete laser therapy, first, by leaving one patent opposite arteriovenous anastomosis from the recipient to the donor and, second, by leaving one patent arteriovenous anastomosis from the donor to the recipient. In both simulations we reproduced the clinical observation of severe hematocrit discordance preceding delayed amniotic fluid imbalance. In conclusion, incomplete laser therapy may cause a severe circulatory imbalance between the twins which presents predominantly as discordant hematocrits rather than discordant amniotic fluid volumes as in primary TTTS. These results imply that the anemia-polycythemia sequence is a sensitive mechanism to identify transfusion reversal after complicated laser therapy, confirming the suggested role of middle cerebral artery peak systolic velocity Doppler measurements as a useful method of follow-up.

Impact of altered loading conditions on ventricular performance in fetuses with congenital cystic adenomatoid malformation and twin-twin transfusion syndrome

OBJECTIVES

In the fetus with a structurally normal heart, two conditions--giant chest mass, such as congenital cystic adenomatoid malformation (CCAM), and twin-twin transfusion syndrome (TTTS)--alter ventricular loading conditions and may result in cardiovascular compromise. The aim of this study was to elucidate the mechanism of cardiovascular dysfunction by comparing geometry-independent, Doppler flow-derived measures of ventricular performance in fetuses with altered loading conditions vs. those in normal fetuses.

METHODS

Doppler flow-derived measures of myocardial performance index (MPI) as described by Tei, ventricular ejection force as described by Isaaz, and combined cardiac output (CCO) were obtained by echocardiography in fetuses with a normal cardiovascular system (n = 76) or CCAM (n = 36) and fetal partners with TTTS (n = 22).

RESULTS

In the CCAM group, systolic performance as evidenced by the ejection forces was preserved, right ventricular (RV) MPI was increased and CCO diminished, suggesting diastolic dysfunction and poor filling secondary to cardiac compression and a tamponade effect. In TTTS, recipient twins exhibited greater left ventricular (LV) ejection forces and higher CCO than donor twins, and had abnormal RV and LV MPI, reflecting increased preload, preserved left systolic performance, but diastolic dysfunction. Donor twins had diminished ejection forces and CCO in comparison with normal controls and recipient partners, reflecting hypovolemia.

CONCLUSIONS

In both CCAM and recipient twins of the TTTS, diastolic dysfunction plays a significant role in the pathophysiology of each disorder and precedes changes in systolic performance. Measures of ventricular performance can help elucidate poorly understood mechanisms of cardiovascular compromise in the developing fetus.

Twin-to-twin transfusion syndrome after 26 weeks of gestation: is there a role for fetoscopic laser surgery?

OBJECTIVE

To compare fetoscopic laser surgery with amniodrainage in the treatment of twin-to-twin transfusion syndrome (TTTS) diagnosed after 26 weeks of gestation.

DESIGN

A retrospective cohort study.

SETTING

Leiden University Medical Centre, a tertiary referral hospital for fetal therapy.

POPULATION

Between January 1991 and February 2006, 21 TTTS cases were diagnosed and treated after 26 weeks of gestation.

METHODS

Treatment of TTTS consisted of either amniodrainage or fetoscopic laser coagulation of vascular anastomoses.

MAIN OUTCOME MEASURES

PRIMARY OUTCOME

adverse outcome (intrauterine or neonatal death, major neonatal morbidity and/or severe cerebral injury). Secondary outcome: gestational age at birth.

RESULTS

Eleven TTTS cases were treated with amniodrainage and ten with laser surgery. Median gestational age at birth in the amniodrainage group and in the laser surgery group was 29 and 31 weeks, respectively (P = 0.17) All infants were born alive. Major neonatal morbidity occurred more often in the amniodrainage group than in the laser surgery group, 27% (6/22) and 0% (0/20), respectively (P = 0.02). Severe cerebral injury in the amniodrainage group and in the laser surgery group occurred in 23% (5/22) and 15% (3/20) of infants, respectively (P = 0.70). Neonatal mortality in the amniodrainage group and in the laser surgery group was 14% (3/22) and 0% (0/20), respectively (P = 0.23). Overall adverse outcome was 36% (8/22) in the amniodrainage group and 15% (3/20) in the laser surgery group (P = 0.17).

CONCLUSION

In TTTS diagnosed after 26 weeks of gestation, amniodrainage and laser surgery both result in 100% survival. However, infants born after laser surgery have less major neonatal morbidity.

Severe twin-twin transfusion syndrome: outcome after fetoscopic laser ablation of the placental vascular equator

OBJECTIVE

To assess the safety and efficacy of a modified fetoscopic laser ablation technique for the management of severe twin-twin transfusion syndrome (TTTS) in a large series of pregnancies.

DESIGN

Prospective cohort study.

SETTING

Tertiary referral fetal medicine unit.

POPULATION

Women with pregnancies complicated by severe TTTS (Quintero stage III or IV), before 26 weeks of gestation.

METHODS

Fetoscopic laser ablation of placental anastomoses was performed. The sonoendoscopic approach was used to identify the placental vascular equator and to photocoagulate crossing vessels.

MAIN OUTCOME MEASURES

Overall survival, fetal and perinatal mortalities, gestational age at delivery, birthweight, operating time and recurrence of TTTS.

RESULTS

A total of 77 women underwent the procedure. The mean gestational age at treatment was 20 (range 16-26) weeks. On average, four vessels were ablated during each procedure, with a mean operative time of 15 (range 5-25) minutes. None of the women required a repeat fetoscopic laser treatment for recurrence of the TTTS. There was at least one survivor in 74% (57/77) of pregnancies, and the overall survival rate was 57% (88/154).

CONCLUSIONS

Fetoscopic laser ablation is a safe and effective form of treatment in the management of severe TTTS. The technique of identifying the common villous district of the placenta by ultrasound and photocoagulating any vessels crossing the vascular equator appears to be an acceptable alternative to both the nonselective and highly selective methods described so far. This approach is associated with a short operating time, low likelihood of TTTS recurrence or fetal anaemia and with survival results that are equivalent to previously reported techniques.

A mathematical model of twin-twin transfusion syndrome with pulsatile arterial circulations

The twin-twin transfusion syndrome (TTTS) is a severe complication of monochorionic twin pregnancies caused by a net transfusion of blood from one twin (the donor) to the other (the recipient) through placental anastomoses. To examine the pathophysiology of TTTS evolving through clinical stages I to IV, we extended our mathematical model to include pulsating circulations propagating along the arterial tree as well as placental and cerebral vascular resistances, and arterial wall thickness and stiffness. The model demonstrates that abnormal umbilical arterial flow (TTTS stage III) in the donor twin results from increased placental resistance as well as reduced resistance in the cerebral arteries. In contrast, recipient twin abnormal umbilical arterial flow requires a significantly greater increase in placental resistance, resulting from the compressive effects of high amniotic fluid pressure. Thus simulated abnormalities of donor umbilical arterial pulsations occur in the donor more commonly and earlier than in the recipient. The “normal” staging sequence (I, II, III, IV) correlates with the presence of compensating placental anastomoses, constituting the majority of monochorionic twin placentas. However, TTTS stage III may occur before manifestations of stage II (lack of donor bladder filling), in our model correlating with severe TTTS from a single arteriovenous anastomosis, an infrequent occurring placental angioarchitecture. In conclusion, this mathematical model describes the onset and development of the four stages of TTTS, reproduces a variety of clinical manifestations, and may contribute to identifying the underlying pathophysiology of the staging sequence in TTTS.

Long-term neurodevelopmental outcome in twin-to-twin transfusion syndrome treated with fetoscopic laser surgery

OBJECTIVE

This study was undertaken to determine the long-term neurodevelopmental outcome in twin-to-twin transfusion syndrome treated with laser.

STUDY DESIGN

All twin-to-twin transfusion syndrome cases treated at our center with laser between August 2000 and December 2003 were included in the study. Neurologic, mental, and psychomotor development at 2 years of age corrected for prematurity was assessed in all twin-to-twin transfusion syndrome survivors. Neurodevelopmental impairment was defined as any of the following: cerebral palsy, deafness, blindness, mental, or psychomotor development index of the Bayley Scales of Infant Development II less than 2 SD.

RESULTS

A total of 82 twin-to-twin transfusion syndrome pregnancies were treated with fetoscopic laser surgery during the study period. Perinatal survival was 70% (115/164). The incidence of neurodevelopmental impairment was 17% (19/115) and was due to cerebral palsy (n = 8), mental developmental delay (n = 9), psychomotor developmental delay (n = 12), and deafness (n = 1).

CONCLUSION

The incidence of neurodevelopmental impairment in twin-to-twin transfusion syndrome survivors treated with laser is high and warrants long-term follow-up.

Regulation of amniotic fluid volume

Water arrives in the mammalian gestation from the maternal circulation across the placenta. It then circulates between the fetal water compartments, including the fetal body compartments, the placenta and the amniotic fluid. Amniotic fluid is created by the flow of fluid from the fetal lung and bladder. A major pathway for amniotic fluid resorption is fetal swallowing; however, in many cases the amounts of fluid produced and absorbed do not balance. A second resorption pathway, the intramembranous pathway (across the amnion to the fetal circulation), has been proposed to explain the maintenance of normal amniotic fluid volume. Amniotic fluid volume is thus a function both of the amount of water transferred to the gestation across the placental membrane, and the flux of water across the amnion. Water flux across biologic membranes may be driven by osmotic or hydrostatic forces; existing data suggest that intramembranous flow in humans is driven by the osmotic difference between the amniotic fluid and the fetal serum. The driving force for placental flow is more controversial, and both forces may be in effect. The mechanism(s) responsible for regulating water flow to and from the amniotic fluid is unknown. In other parts of the body, notably the kidney, water flux is regulated by the expression of aquaporin water channels on the cell membrane. We hypothesize that aquaporins have a role in regulating water flux across both the amnion and the placenta, and present evidence in support of this theory. Current knowledge of gestational water flow is sufficient to allow prediction of fetal outcome when water flow is abnormal, as in twin-twin transfusion syndrome. Further insight into these mechanisms may allow novel treatments for amniotic fluid volume abnormalities with resultant improvement in clinical outcome.

Twin-Twin Transfusion Syndrome Modeling

The twin-twin transfusion syndrome (TTTS) is a severe complication occurring in monochorionic twins, and untreated, causes high rates of mortality and morbidity. In TTTS, five consecutive stages of increasing severity can be distinguished: first, the oligopolyhydramnios sequence; second, anuria in the donor twin; third, abnormal flow waves in either twin; fourth, a hydropic recipient, and finally the fifth stage, fetal demise of either twin. Recently, we developed a mathematical model of the Stages I-IV. In this report, we investigated the influence of amnioreduction and laser therapy at two different gestational ages on the resolution of TTTS Stage III. Simulations were performed for two gestational ages, at 22 and 28 weeks; that is, at the onset of a stuck donor twin and when TTTS has progressed to an anuric donor with abnormal umbilical flow waves and a hydropic recipient, respectively. Results indicate abnormal umbilical flow waves in the donor to resolve rapidly after both amnioreduction and laser therapy. TTTS and abnormal umbilical flows in the donor, however, return after amnioreduction. Laser therapy, leading to cessation of fetofetal transfusion, produces complete resolution of TTTS sequelae, however, with increased vascular stiffness in the donor. Amnioreduction and laser therapy both produce rapid resolution of abnormal umbilical flows in a mathematical model of TTTS. Laser ablation of all anastomoses, however, completely ceases the fetofetal transfusion, so that no TTTS redevelops. In the donor, vascular stiffness remains increased after laser, suggesting increased pulse wave velocities can be measured clinically.

Fetoscopic laser surgery in 100 pregnancies with severe twin-to-twin transfusion syndrome in the Netherlands

OBJECTIVE

In this prospective cohort study, we evaluated the initial results of fetoscopic laser surgery for severe second trimester twin-to-twin transfusion syndrome (TTTS) treated at our centre.

METHOD

A total of 100 consecutive pregnancies with severe second trimester TTTS treated at our centre with selective fetoscopic laser coagulation of vascular anastomoses on the placental surface between August 2000 and November 2004 were included in the study. Perinatal survival was analysed in relation to Quintero stage.

RESULTS

Median gestational age was 20 weeks at fetoscopy (range: 16-26) and 33 weeks at delivery (range: 18-40). Perinatal survival rate was 70% (139/200). The treatment resulted in at least one survivor at the age of 4 weeks in 81% of pregnancies. Perinatal survival was significantly higher when treatment was performed in the early Quintero stages (95% in stage 1, 76% in stage 2, 70% in stage 3, 50% in stage 4) (p = 0.02).

CONCLUSION

Results of fetoscopic laser surgery for TTTS in our centre are similar to those in specialised centres in other countries. Diagnosis and treatment in the early Quintero stages resulted in significantly higher perinatal survival.

Deep-hidden anastomoses in monochorionic twin placentae are harmless

OBJECTIVES

Our objective was to identify the clinical consequences of deep-hidden anastomoses that occur underneath the placental surface.

METHODS

Twelve placentae that underwent intrauterine laser ablation of placental anastomoses for twin-twin transfusion syndrome (TTTS) and 14 non-TTTS controls were investigated for deep-hidden anastomoses. Additionally, we investigated the inter-twin haemoglobin differences as an indicator for fetofetal transfusion. Placentae were divided into four groups: TTTS placentae without residual chorionic-plate anastomoses without deep-hidden anastomoses (group 1) and with deep-hidden anastomoses (group 2), and non-TTTS placentae with chorionic-plate anastomoses without deep-hidden anastomoses (group 3) and with deep-hidden anastomoses (group 4).

RESULTS

Deep-hidden anastomoses were identified in 58% (7/12) of the TTTS placentae after laser surgery and in 64% (9/14) of the non-TTTS placentae. Groups 1 and 2 had equal inter-twin haemoglobin differences: medians 1.4 and 1.2 gr/dL, respectively (p = 0.48). In group 3, the median inter-twin haemoglobin difference without deep-hidden anastomoses was 2.6 gr/dL (group 3) and with deep-hidden anastomoses (group 4) it was 5.1 gr/dL (p = 0.26).

CONCLUSION

Both comparisons imply that deep-hidden anastomoses did not cause any additional increase in Hb difference. In conclusion, haematological and additional hemodynamical analysis show that deep-hidden anastomoses are likely to occur without any clinical consequences.

Perinatal loss among twins

OBJECTIVE

We evaluated prenatal factors related to perinatal loss in twins, using medical records and death certificates, to determine the main perinatal event that contributed to babies' deaths.

DESIGN

This was a retrospective cohort study of 550 monochorionic diamniotic or diamniotic dichorionic twins who were delivered at Kaiser Permanente Colorado between 1994 and 2001.

MAIN OUTCOME

The main outcome of the study was perinatal loss (stillbirth or neonatal death).

OUTCOMES MEASURES

Select maternal risk factors (maternal age, race, marital status, assisted conception, past history of preterm birth, cigarette smoking, and placentation) were included in the univariable and multivariable logistic regression analysis. Data on these risk factors came from review of records from our multiple-birth perinatal database. A comprehensive review of clinical events recorded in the medical records and on the death certificate was conducted to assess the main event that contributed to the loss.

RESULTS

In the cohort of 1100 babies, there were 12 stillbirths and 34 neonatal deaths, with an overall frequency of perinatal loss of 4.2%. We found a strong association between a monochorionic diamniotic placentation and perinatal loss (adjusted odds ratio, 3.9; 95% confidence interval, 2, 7.7). At delivery, placental pathology and spontaneous preterm birth accounted for 36% and 41%, respectively, of the clinical events contributing to the demises. Compared with the medical record, review of death certificate information did not contribute significantly to the understanding of the sequence of perinatal events leading to the demise.

CONCLUSIONS

We conclude that loss in twins is most strongly associated with monochorionic diamniotic placentation. Although this condition is not preventable, early identification (by ultrasound) and referral to subspecialists may decrease the chances of perinatal loss. Prevention of spontaneous preterm birth in all women remains an important initiative in obstetric care to reduce perinatal mortality and neonatal morbidity. We believe that improvements in the reporting on death certificates will allow future research on large data sets and may provide further insight into perinatal loss in twins. We emphasize the importance of a comprehensive clinical review of each case of perinatal loss to fully understand the sequence of clinical events leading to this adverse pregnancy outcome.

Abnormal arterial flows by a distributed model of the fetal circulation

Modeling the propagation of blood pressure and flow along the fetoplacental arterial tree may improve interpretation of abnormal flow velocity waveforms in fetuses. The current models, however, either do not include a wide range of gestational ages or do not account for variation in anatomical, vascular, or rheological parameters. We developed a mathematical model of the pulsating fetoumbilical arterial circulation using Womersley's oscillatory flow theory and viscoelastic arterial wall properties. Arterial flow waves are calculated at different arterial locations from which the pulsatility index (PI) can be determined. We varied blood viscosity, placental and brain resistances, placental compliance, heart rate, stiffness of the arterial wall, and length of the umbilical arteries. The PI increases in the umbilical artery and decreases in the cerebral arteries, as a result of increasing placental resistance or decreasing brain resistance. Both changes in resistance decrease the flow through the placenta. An increased arterial stiffness increases the PIs in the entire fetoplacental circulation. Blood viscosity and peripheral bed compliance have limited influence on the flow profiles. Bradycardia and tachycardia increase and decrease the PI in all arteries, respectively. Umbilical arterial length has limited influence on the PI but affects the mean arterial pressure at the placental cord insertion. The model may improve the interpretation of arterial flow pulsations and thus may advance both the understanding of pathophysiological processes and clinical management.

Hypothesis: The Placental ‘Steal’ Phenomenon – A Possible Hazard of Amnioreduction

The twin-twin transfusion syndrome (TTTS) complicates approximately 15% of monochorionic twin pregnancies. Severe TTTS is associated with poor neonatal outcome and a relatively high rate of neurological abnormalities. Some studies have suggested this outcome to be more severe in cases treated by amnioreduction. In this paper we present a hypothesis that radical amnioreduction performed after 24 weeks of gestation might cause a shift of blood from the fetus into the placenta. This could explain some of the severe neurological outcomes, such as hypoxic ischemic brain damage, seen in these cases.

Intertwin anastomoses in monochorionic placentas after fetoscopic laser coagulation for twin-to-twin transfusion syndrome: is there more than meets the eye?

OBJECTIVE

This study was undertaken to detect missed anastomoses on the chorionic surface as well as hidden connections in the depth of the cotyledons in placentas after laser coagulation for twin-to-twin transfusion syndrome (TTTS) and to correlate these findings to clinical outcome.

STUDY DESIGN

All cord vessels were injected with dyed barium sulphate. A digital photograph of the chorionic surface angioarchitecture and single-shot digital X-ray (Rx) angiograms were made. The presence and diameter of any missed anastomoses on the chorionic surface and of any hidden angiographic connections were determined.

RESULTS

Fifty placentas were analyzed, 7 of double intrauterine fetal death (IUFD) and 43 of double survivors. In 9 of 43 (21%) cases with double survival and in all 7 cases of double IUFD, missed anastomoses were identified that should have been ablated by laser coagulation (P < .001). There appeared to be a correlation between the type and diameter of missed anastomoses on the chorionic surface and the clinical outcome. Placentas with missed large arteriovenous/venoarterial anastomoses (AV/VA) (N = 8) were from cases with recurrent TTTS or double IUFD (unless compensated by a large arterioarterial anastomosis [AA]). Next, missed small AV/VA (N = 4) without AA resulted in isolated (ie, without TTTS) discordant hemoglobin levels requiring intrauterine transfusion. Finally, when there were no missed anastomoses (N = 34), TTTS had resolved in all cases and outcome was good, although 1 case had discordant hemoglobin values treated with a single intrauterine transfusion and 4 others had discordant hemoglobin at birth. On Rx angiography, potential hidden connections were present, all but 1 case.

CONCLUSION

Coagulation of all anastomoses visible on the chorionic surface seems adequate to treat TTTS. However, hidden connections in the depth of the cotyledon could not be excluded and may be involved in lesser degrees of intertwin transfusion.

Simulation of therapy in a model of a nonhydropic and hydropic recipient in twin-twin transfusion syndrome

OBJECTIVE

This study was undertaken to model the sequence of events that occurs after amnioreduction, laser therapy, and digoxin administration in twin-twin transfusion syndrome (TTTS) with and without a hydropic recipient twin.

STUDY DESIGN

We added amnioreduction, laser therapy, and digoxin administration to our mathematical TTTS model and simulated combinations of these therapies.

RESULTS

With a nonhydropic recipient, simulated amnioreduction delays the onset of hydrops. Conversely, with a hydropic recipient, amnioreduction aggravates the degree of hydrops. Furthermore, amnioreduction increases the transplacental fluid flow and may temporarily cause a hydropic donor. Laser therapy terminates the cause of recipient hydrops. Digoxin reduces the degree of recipient hydrops, but increases arteriovenous fetofetal transfusion.

CONCLUSION

Laser therapy is superior in TTTS with a hydropic recipient, because simulated amnioreduction aggravates the recipient's cardiovascular status. Digoxin benefits a hydropic recipient but slightly worsens the donor's condition. Therefore, TTTS presenting with a hydropic recipient prior to fetal viability (approximately 26 weeks) may be best treated with laser therapy, whereas more advanced gestations may be offered digoxin administration plus amnioreduction, to delay the progression of TTTS.

Current concepts in fetal cardiovascular disease

This article discusses the unique properties of the fetal cardiovascular system and patterns of blood flow in congenital heart disease. It also explores the complex interactive dependency between the developing heart and pulmonary vasculature, with particular attention to hypoplastic left heart syndrome. The article goes on to highlight some recent advances in the understanding of fetal cardiovascular medicine, specifically the possibilities and prognosis for fetal cardiac interventions. An understanding of the enigmatic process of twin-twin transfusion syndrome may help in elucidating one of the mechanisms for development of cardiac structural abnormalities in the fetus.

Monochorionic diamniotic infants without twin-to-twin transfusion syndrome

BACKGROUND

Monochorionic-diamniotic twins (MoDi) occur in 0.3% of all pregnancies. Twin-to-twin transfusion syndrome (TTS) that occurs in 20% of MoDi pregnancies is associated with high perinatal morbidity and mortality. MoDi twins without TTS are more frequent (80%) but have been scarcely reported.

OBJECTIVE

To study perinatal morbidity and mortality of 74 MoDi twin sets without TTS and to compare it to that of 38 sets of MoDi twins with TTS.

METHODS

Chorionicity was determined by gender and placental examination. Gestational age (GA) was set by sonography and pediatric examination. TTS was diagnosed clinically and by sonography, discordance was defined by twins birth weight difference > or =20%, and fetal growth restriction was determined by using a twin-specific nomogram.

RESULTS

MoDi twin pregnancies without and with TTS were similar in demographics, live births, history of preeclampsia, fetal distress and cesarean delivery. They were different (p<0.01) in discordant pregnancies (36 and 79%), GA at delivery (32 and 29 weeks) intrauterine growth restriction (39 and 89%) and neonatal mortality (12 and 36%). Concordant (47 sets) and discordant (27 sets) MoDi twins without TTS were clinically similar.

CONCLUSIONS

MoDi twins without TTS have high rates of birth weight discordance, fetal growth restriction, fetal distress, prematurity and cesarean delivery. Although their perinatal mortality is low, the reported occurrence and the short- and long-term impacts of fetal and neonatal morbidities warrants attention.

Neonatal outcome in twin-to-twin transfusion syndrome treated with fetoscopic laser occlusion of vascular anastomoses

OBJECTIVE

To determine neonatal mortality and morbidity rates in monochorionic twins with chronic twin-to-twin transfusion syndrome (TTTS) treated with fetoscopic laser occlusion of vascular anastomoses.

STUDY DESIGN

In a prospective study of monochorionic twins delivered at our center between June 2002 and December 2004, neonatal outcome was assessed in 40 monochorionic twin pairs with TTTS treated with laser compared with 46 monochorionic twin pairs without TTTS.

RESULTS

The neonatal mortality rate in the TTTS and no-TTTS group was 8% (6/76) and 3% (3/90), respectively. The rate of severe cerebral lesions on ultrasound scanning in the TTTS and no-TTTS group was 14% (10/72) and 6% (5/82), respectively. The incidence of adverse neonatal outcome (neonatal death, major neonatal morbidity, or severe cerebral lesions) in the TTTS and no-TTTS group was, respectively, 26% (20/76) and 13% (12/90) (RR = 1.97, 95% CI = 1.03 to 3.77).

CONCLUSIONS

Although perinatal outcome in TTTS has improved after laser therapy, neonatal mortality and morbidity rates remain high. Relative risk for adverse neonatal outcome is increased 2-fold in TTTS treated with laser relative to monochorionic twins without TTTS.

Monochorionic triplet pregnancy complicated by severe fetofetal transfusion

We report two cases of fetofetal transfusion in monochorionic triamniotic triplet pregnancies. Case 1: At 23 weeks' gestation an amnioreduction was carried out. Three days later, the donor triplet died in utero. Immediately after that, a cardiotocogram of the triplet who had been thought to be unaffected by the fetofetal transfusion, showed a non-reassuring fetal status. Although cesarean section was carried out, none of the triplets survived. Case 2: At 24 weeks' gestation a woman was transferred to our center because of fetofetal transfusion in monochorionic triplets. Cesarean section was carried out. However, the recipient died on the 75th day after birth, and the others had neurological problems. Previous reports on fetofetal transfusion in triplets are very limited. The prognosis of this condition has been reported to be severe, irrespective of chorionicity, gestational age at delivery, maternal age, and parity. When managing a monochorionic or dichorionic triplet pregnancy, serial and careful ultrasound examination is mandatory to find early symptoms of this serious condition.

Modeling a hydropic recipient twin in twin-twin transfusion syndrome

We developed a mathematical model of twin-twin transfusion syndrome (TTTS) that includes a hydropic recipient twin, adding interstitial and intracellular fluid compartments, fetal congestive cardiac failure, and the dynamics of renin-angiotensin system (RAS) mediators to our previous TTTS model. Ten differential equations for each twin, coupled by the net fetofetal transfusion of blood and blood components, i.e., colloids, osmoles, and RAS mediators, describe the development of fetal arterial and venous blood volumes, blood osmolality and colloid osmotic pressure (COP), interstitial fluid volume and COP, intracellular fluid volume, amniotic fluid volume and osmolality, and RAS mediator concentration. We included varying placental anastomoses, placental sharing, and amnionicity. The 20 differential equations were solved numerically from 0 to 40 wk with a 0.6-s time step. Consistent with clinical experience, model predictions are as follows. Unidirectional arteriovenous anastomoses and arteriovenous anastomoses inadequately compensated by oppositely directed anastomoses cause severe TTTS that includes a hydropic recipient. Adequately compensated arteriovenous anastomoses simulated TTTS without hydrops. The probability that oppositely directed anastomoses prevent onset of a hydropic recipient after TTTS onset, i.e., the largest interval between onset of TTTS and onset of hydrops in the recipient, was best for a venovenous anastomosis, closely followed by an arterioarterial and finally an oppositely directed arteriovenous anastomosis. Hydropic recipients have decreased amniotic fluid volume. Unequal placental sharing and amnionicity modify hydrops onset. In conclusion, our model simulates a sequence of events that results in a hydropic recipient twin in severe TTTS. The model may allow an assessment of the efficacy of current therapeutic interventions for TTTS cases that include a hydropic recipient twin.

Management of fetofetal transfusion syndrome

Feto-fetal transfusion syndrome contributes heavily to high rates of perinatal mortality and morbidity in monochorionic multiple pregnancies. Its prenatal management has been controversial for at least 25 years. We review the recent literature in order to present the basis for a pragmatic reappraisal of the management of this condition. Laser surgery of the chorionic plate inter-twin anastomoses is the best first-line treatment when the syndrome develops before 26 weeks' gestation. Survival (including quality of survival) and gestational age at delivery are improved when compared to serial amnioreduction. Second-line treatment options include repeat-laser, intra-uterine blood transfusion, serial amnioreduction, selective feticide using bipolar cord coagulation or elective delivery, depending upon gestational age and the severity of the disease and its complications. We have found that fetoscopic placental surgery has proven itself over simplicity of amnioreduction. There is no evidence that treatment should be customized according to the stage of the disease at diagnosis. Early recognition of the syndrome through fortnightly serial ultrasound follow-up of all monochorionic pregnancies should ensure timely referral and make up for geographical constraints. Laser surgery should now be available in fetal medicine units that are managing at least 20 cases per year.

Insights into the pathophysiology of twin–twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) is attributed to trans-anastomotic transfusion between twins. Anastomoses are ubiquitous in monochorionic (MC) placentae, yet TTTS develops in only 15%. Although ex vivo and in vivo studies fail to identify a unique anastomotic signature, TTTS placentae are typically associated with an imbalance in unidirectional arteriovenous anastomoses with absent bidirectional anastomoses. Doppler detection of an artery-artery anastomosis reduces the chance of TTTS, whereas, in those that develop the disease, it improves stage-independent survival. Selective laser is often curative, but an increasingly recognized risk of persistent or reverse TTTS may be attributable to atypical arteriovenous anastomoses not identifiable from the chorionic plate. Simple dysvolaemia fails to explain several phenotypic features, including haematological concordancy, recipient hypertension, and reversibly absent end diastolic flow in the donor. The renin-angiotensin system is upregulated in the donor and downregulated in the recipient's kidneys, while paradoxically raised renin levels in the recipient may contribute to raised afterload along with endothelin. Although research is limited in humans by therapy and the lack of a suitable experimental model, further studies of placental and vascular pathophysiology may not only refine current treatment modalities but may also, in addition, suggest further avenues for downstream management such as genetic predisposition testing or pharmacological intervention.

Twin–Twin Transfusion Syndrome: A Population-Based Study

OBJECTIVE

To study the incidence and mortality and morbidity rates of twin-twin transfusion syndrome in a complete population-based cohort in Nova Scotia.

METHODS

A population-based cohort study of all monochorionic diamniotic twin pregnancies of 20 weeks of gestation or longer born to Nova Scotia (Canada) residents between 1988 and 2000 was examined. The effect of gestational age adjustment and birth weight discordancy of more than 20% on mortality and 1-year survival was studied. Other outcomes studied included birth depression, respiratory distress syndrome, chronic lung disease, interventricular hemorrhage, periventricular leukomalacia, acute renal failure, and congestive heart failure.

RESULTS

Of 404 monochorionic-diamniotic twin pregnancies examined, 48 were identified with twin-twin transfusion syndrome. Total mortality rates per pregnancy were significantly greater in the twin-twin transfusion syndrome group than in the remainder of our monochorionic diamniotic population (P < .01). However, when adjusted for gestational age, mortality failed to achieve statistical significance. Similarly, no differences were noted for 1-year survival and other outcomes of liveborn infants after gestational age adjustment. Discordance in birth weight predicted a higher incidence of morbid outcomes per pregnancy, but this effect was lost after gestational age adjustment.

CONCLUSION

Increased morbidity and mortality of twins with twin-twin transfusion syndrome is likely to be due to a higher incidence of preterm birth. Birth weight discordancy was not found to be an independent predictor of mortality after controlling for gestational age and twin-twin transfusion syndrome.

Successful patching of iatrogenic rupture of the fetal membranes

Rupture of the fetal membranes is a common, but potentially serious complication of invasive fetal procedures. Quintero described a technique to seal the fetal membrane defect by means of a bloodpatch, usually called 'amniopatch' in this application. The successful use in two consecutive patients with ruptured membranes after a fetoscopic intervention at respectively 17 and 22 weeks' gestational age is described, together with a literature review of published experience.

How can we diagnose and manage twin–twin transfusion syndrome?

Severe mid-trimester twin-twin transfusion syndrome (TTS) complicates about 15% of monochorionic twin pregnancies. If left untreated, the mortality is 80-100%. The pathophysiological prerequisite for the onset of TTS is unequal blood flow via arteriovenous placental anastomoses from the so-called donor to the recipient twin. This can result in hypovolemia, hypotension and oligo- or anuria in the donor, and hypervolemia, hypertension, polyuria and finally heart failure in the recipient. Leading sonographic signs of TTS include severe oligo- or anhydramnios and a small or absent bladder filling in the donor in contrast to polyhydramnios with increased bladder filling in the recipient. Patients might present with clinical symptoms due to massive polyhydramnios. In severe mid-trimester TTS, fetoscopic laser occlusion of the anastomosing vessels on the placental surface under local anaesthesia plus subsequent amniodrainage is the most promising therapeutic option at present. In acute TTS after 26 weeks of gestation, amniodrainage is the therapy of choice. All patients suspected of this high-risk condition should be referred to a specialized fetal medicine centre.

Differential diagnosis and management of anemia in the newborn

Neonatal anemia is a condition with a diverse etiologic spectrum.Therefore, in order to form a focused differential diagnosis, it is important for the caregiver to have some knowledge of the more common causes of low hemoglobin and hematocrit concentrations in the neonate. Proper history taking, physical examination, and interpretation of diagnostic tests can narrow this focus and aid in establishing an accurate diagnosis and in directing the appropriate therapeutic interventions.

Twin-twin transfusion syndrome treated with serial amniocenteses

BACKGROUND

To evaluate the treatment and neonatal outcome in pregnancies complicated by twin-twin transfusion syndrome (TTS).

MATERIAL AND METHODS

Twenty-four women with TTS were identified in the period 1993-99 among 34477 deliveries. We include a retrospective chart review of all twins with TTS.

RESULTS

The overall incidence of TTS was 4.75% of all twin pregnancies. The mean gestational age at the time of diagnosing TTS was 23 weeks (range 17.6-38), and the mean gestational age at delivery was 34.6 weeks (range 23.1-38.3). Therapeutic amniocenteses was performed in 21 women. The total volume drained varied from 0.4 to 32.31 with a mean of 2.3 l. Overall perinatal mortality in TTS was 35.4%, as nine donor twins and eight recipient twins died. The main causes for mortality were intrauterine death and prematurity.

CONCLUSION

Twin-twin transfusion syndrome is a severe complication in monochorionic diamniotic twin pregnancies, with high perinatal mortality and morbidity even though amnioreduction prolonged the pregnancies leading to better neonatal outcome.

Influence of vasopressin in the pathogenesis of oligohydramnios–polyhydramnios in monochorionic twins

OBJECTIVES

The pathophysiology of oligohydramnios-polyhydramnios in monochorionic (MC) twins complicated by chronic twin-twin transfusion syndrome (TTTS) is poorly understood. We hypothesise that oliguria and oligohydramnios in the donor twin of chronic TTTS, occurs due to antidiuretic and vasoconstrictive activity of vasopressin (AVP).

METHODS

We measured AVP levels in maternal, fetal and amniotic fluid samples obtained in utero and at birth from 44 MC twins with (n=27) or without chronic TTTS (n=17). Concentrations of AVP in pg/ml were determined by immuno-radiometry assay.

RESULTS

In donor fetuses, plasma and amniotic fluid AVP levels were higher than those of the recipient twins in utero (P<0.001) and at birth (P<0.001). No such differences were found between the non-TTTS twins. The plasma AVP concentrations were higher in the recipient fetuses with severe hydrops than those without hydrops (2.8+/-0.7 pg/ml versus 0.3+/-0.3 pg/ml; P<0.05). Maternal AVP levels were comparable between the TTTS and non-TTTS groups. In the non-TTTS twins, both plasma and amniotic fluid AVP levels were higher than those of the recipient twins (P<0.001) but lower than those of the donor twins (P<0.001). There was a significant association between amniotic fluid and plasma AVP levels both in the TTTS (r=0.78; P<0.001) and non-TTTS (r=0.70; P<0.01) infants.

CONCLUSIONS

Vasopressin concentrations in the donor twins were three times higher than their co-twins which suggests that oligohydramnios may occur as a consequence of AVP mediated reduction in fetal urine output.