Gestational diabetes mellitus diagnosed by screening or symptoms: does it matter?

Twin-twin transfusion syndrome (TTTS) is present in approximately 5–15% of monochorionic-diamniotic twin pregnancies. A chronic blood flow imbalance through placental vascular anastomoses from the donor to the recipient twin is considered the pathophysiologic mechanism responsible for the development of TTTS. Discordant echogenicity between the donor and recipient placenta has been proposed in a previous case report as an additional sonographic sign of TTTS. Here, we present a case of TTTS with discordant placental echogenicity characterized by a hyperechoic and thicker placental side in the donor twin associated with reduced vascular Doppler signals, histologic lesions suggestive of ischemic changes, and overexpression of anti-angiogenic factors.     

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.     

Monochorialität: Risiken und intrauterine Therapie

Monochorionic twin pregnancies are at increased risk for certain complications owing to placental vascular anastomoses. This review describes the various types of angioarchitecture of monochorionic placentas and their consequences for the natural history of these pregnancies as well as for intrauterine invasive procedures. In cases of unequal placental sharing, many anastomoses exist and usually include large arterio-arterial anastomoses. This is typical for early-onset discordant growth, and the smaller twin may benefit from monochorionicity. In cases of late-onset discordant growth, the placentas are usually equally shared, and there are fewer and smaller anastomoses. Severe midtrimester twin-to-twin transfusion syndrome occurs in about 10% of monochorionic pregnancies, and severe discordant growth without transfusion syndrome occurs in 14%. Fetoscopic laser coagulation of placental vascular anastomoses in twin-to-twin transfusion syndrome results in significantly improved outcomes compared with other therapeutic interventions such as serial amniodrainage. In cases of selective intrauterine growth restriction, the optimal time for elective preterm delivery should be based on the results of intensive fetal monitoring. Cord coagulation of a twin with severe complications leads to survival rates of more than 80% for co-twins.     

Actual treatment options of twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome -TTTS is observed in 10-15% of monochorionic twin pregnancies. The pathogenesis of the syndrome is still unknown, and the mortality reaches 80-90% if not treated. There are two invasive treatment options of TTTS: Fetoscopic laser coagulation of the placental anastomoses and serial amniodrainages. Endoscopic laser coagulation of anastomoses is a more effective first-line treatment than serial amnioreduction for severe TTTS. The rate of major neurologic complications is higher in amnioreduction group, than in Fetoscopic group.     

Management of twin–twin transfusion syndrome

This paper presents a review of the diagnosis and treatment of twin-to-twin transfusion syndrome (TTTS). The incidence of fetal or neonatal mortality and preterm delivery in monochorionic twin pregnancies is substantially much higher than in dichorionic twin pregnancies due to TTTS. About 15% of all monochorionic twin pregnancies are affected by severe TTTS which is characterized by hypervolemia and polyhydramnios in one fetus and hypovolemia and anhydramnios in the other one. It is caused by vascular anastomoses within the shared placental system. With close surveillance without intervention, the majority of these pregnancies result in fetal death of both fetuses. Effective treatment is provided by intrauterine laser coagulation of the communicating vessels, allowing survival of at least one fetus in about 75% of the cases.     

Fetofetal transfusion syndrome in triplet pregnancies: outcome after endoscopic laser surgery

OBJECTIVE: The purpose of this study was to determine the outcome of fetofetal transfusion syndrome in triplet pregnancies after treatment with endoscopic laser ablation of communicating placental vessels. STUDY DESIGN: Cases of severe fetofetal transfusion syndrome that occur in triplet pregnancies and that are treated with endoscopic laser ablation of placental anastomosis were identified from a prospectively collected fetal medicine database. Chorionicity was determined by sonography and classified as dichorionic or monochorionic. Perinatal outcome was obtained in all cases, and long-term follow-up was obtained in all pregnancies that resulted in at least 1 survivor. RESULTS: During a 6-year period, 10 cases of severe fetofetal transfusion syndrome that were treated with endoscopic laser ablation were identified, of which 7 cases were dichorionic and 3 cases were monochorionic. At least 1 fetus survived in all 7 dichorionic pregnancies and in 2 of the 3 monochorionic pregnancies. In the dichorionic pregnancies, 14 of 21 fetuses (66.7%) survived, but in the monochorionic pregnancies only 2 of 9 fetuses (22.2%) survived. CONCLUSION: Endoscopic laser ablation is feasible in triplet pregnancies that are complicated by severe fetofetal transfusion syndrome. The treatment appears to be associated with improved perinatal outcome in dichorionic, but not in monochorionic, triplets, probably because of the technical inability in achieving ablation of all the communicating vessels in monochorionic triplets.     

Fetal circulation and placental blood flow in monochorionic twins

Objectives. Twin to twin transfusion syndrome (TTTS) is one of the most important problems for perinatal management of monochorionic twins. Since TTTS is deeply related to the prognoses of both fetuses, fetal circulation and placental blood flow of monochorionic twins were studied with the purpose of clarifying characteristic features.

Methods. The patterns and numbers of vascular anastomoses were checked on the placental surface, arterio-arterial (A-A) anastomosed vessels by ultrasound, and circulatory changes were studied with relation to uterine contraction.

Results. The high risk of monochorionic twin pregnancies was largely related to the patterns of vascular anatomy of the placenta and numbers of anastomosed vessels. The first placental vascular connection detected in vivo was the A-A anastomosis characterized by the bidirectional flow waveform in pulsed Doppler velocimetry.

Conclusion. TTTS is related to anastomosed vessels on the surface of placenta. To manage and prevent TTTS, fetal circulation and placental blood flow should be carefully observed.     

Placental magnetic resonance imaging in monochorionic twin pregnancies

Objective: Twin-twin transfusion syndrome (TTTS) is a severe complication of monochorionic pregnancies. Placental hydrops might be a marker for TTTS. The purpose of this study was to evaluate whether differences in the placental parenchyma due to TTTS can be seen with fetal MRI. Methods: In a retrospective study, 34 monochorionic pregnancies were investigated on a 1.5 Tesla MR. Seventeen pregnancies were affected by TTTS, and 17 showed no clinical signs of TTTS. Placental maturation and vascular pathologies, as well as the extent of the placental findings and allocation of placental tissue to each twin, were investigated. Placental findings were reported for origin, size, maturation, and placental thickness, and were correlated with the presence of TTTS. Results: All placentas affected by TTTS showed abnormal maturation on MR scans, but only 64.7% of the non-TTTS group (p?=?0.018). Vascular placental pathologies did not differ significantly between the TTTS and non-TTTS group. Conclusions: MR-signs of placental maturity in monochorionic twin pregnancies may indicate a lower risk of development of TTTS.     

Individual placental territories after selective laser photocoagulation of communicating vessels in twin-twin transfusion syndrome

OBJECTIVE: Intrauterine fetal death of one or both twins after laser therapy (selective photocoagulation of communicating vessels) may occur, in part, from insufficient individual placental mass. The objective of this study was to assess the percentage of individual placental mass (individual placental territory) that is associated with fetal survival in twin-twin transfusion syndrome after selective photocoagulation of communicating vessels. STUDY DESIGN: Placentas from 72 patients with selective photocoagulation of communicating vessels-treated twin-twin transfusion syndrome without intrauterine fetal death and from 61 monochorionic pregnancies without twin-twin transfusion syndrome (control subjects) were assessed. The placentas were weighed fresh (total placental mass) and cut along the vascular equator, which yielded the individual placental mass and the individual placental territory. Patency of anastomoses was ruled out with air-injection. The individual fetoplacental ratio was obtained by dividing birth weight by the corresponding individual placental mass. RESULTS: The 5th percentile individual placental territory that was associated with fetal survival was 27% in control subjects and 18% in cases with twin-twin transfusion syndrome, with a minimum of 10% to 14%, respectively. There were no differences in total placental mass, individual placental mass, individual placental territory, or individual fetoplacental ratio between pregnancies with twin-twin transfusion syndrome and control subjects. However, corrected for gestational age, the birth weight of recipient and donor twins were significantly smaller than control subjects. The individual placental territory of donors was statistically smaller than that of recipients. Individual placental territories were not different within control subjects. CONCLUSION: Fetal survival typically is associated with at least 18% of individual placental territory after selective photocoagulation of communicating vessels for twin-twin transfusion syndrome, but it can occur with as little as 10% to 14% individual placental territory. Decreased birth weight of the donor twin could result from relative decreased percentage of individual placental territory or from the loss of nutrients to the recipient twin. Decreased birth weight of the recipient twin could result from partial deprivation of functional placental tissue after surgery. Our findings may contribute to the understanding of normal and pathologic monochorionic twin gestations, in the counseling of patients, and potentially to the improvement of surgical treatment of twin-twin transfusion syndrome.     

Twin-to-twin transfusion syndrome: what are appropriate diagnostic criteria?

One hundred seventy-eight consecutive twin pregnancies were studied to reevaluate the standard diagnostic criteria for chronic twin-to-twin transfusion syndrome of an intertwin hemoglobin difference greater than 5 gm/dl and a birth weight difference greater than 20%. Hemoglobin differences greater than 5 gm/dl were found in six pregnancies with monochorionic placentas but also in seven with dichorionic placentas. Birth weight differences greater than 20% occurred no more commonly in monochorionic than in dichorionic pregnancies. Of the four pregnancies with a coexisting hemoglobin difference greater than 5 gm/dl and birth weight difference greater than 20%, only one had a monochorionic placenta and therefore likelihood of vascular anastomoses. Diagnosis of twin-to-twin transfusion syndrome cannot be definitively established by current standard diagnostic criteria.     

Search for hemodynamic compromise at 11-14 weeks in monochorionic twin pregnancy: is abnormal flow in the ductus venosus predictive of twin-twin transfusion syndrome?

BACKGROUND AND OBJECTIVES: Twin-twin transfusion syndrome is a devastating complication of monochorionic twin pregnancies. The presence of increased nuchal translucency thickness (NT) in one of the monochorionic twins has been associated with an increased risk of developing this syndrome. One of the most plausible mechanisms for increased nuchal translucency is heart failure, indirectly manifested by abnormal blood flow in the ductus venosus. We aimed to clarify the pathophysiology of increased NT found more frequently in monochorionic twins prone to develop twin-twin transfusion syndrome. DESIGN: We present 50 cases of monochorionic twin pregnancies in which nuchal translucency thickness was measured and ductus venosus blood flow evaluation was performed at 11-14 weeks of gestation. RESULTS: Whenever the fetuses of a twin pregnancy were found to have discrepant nuchal translucency thickness measurements and abnormal flow in the ductus venosus was found in the fetus with increased nuchal translucency thickness, twin-twin transfusion syndrome eventually developed. Progression to twin-to-twin transfusion syndrome was not observed in the twins displaying no intertwin difference in nuchal translucency thickness measurements and it was not observed in those with discrepant nuchal translucency thickness but normal flow in the ductus venosus of both fetuses. In the two cases which developed twin-to-twin transfusion syndrome, fetoscopic laser coagulation of the vascular anastomoses was successfully carried out at 18 weeks and normalization of the venous return was recorded. CONCLUSIONS: Both increased nuchal translucency and abnormal flow in the ductus venosus in monochorionic twins may be early manifestations of haemodynamic imbalance between donor and recipient. The combined evaluation of both parameters in monochorionic twin pregnancies may constitute an effective method for identifying those at risk of developing twin-to-twin transfusion syndrome.     

Twin pregnancy

Twins account for 2–3% of all births. They carry significant risks to both mothers and babies. These risks include preterm delivery, intrauterine growth restriction and pre-eclampsia. In addition, monochorionic gestations confer an even higher rate of perinatal morbidity and mortality arising from a shared placenta due to placental anastomoses, which may lead to twin to twin transfusion syndrome (TTTS). It is essential that chorionicity is established in the first trimester in order to initiate the appropriate antenatal management and surveillance. In view of the high risk of both maternal and fetal complications, twin pregnancies are ideally managed in a dedicated clinic according to agreed protocols.     

Long-term outcome after intrauterine laser treatment for twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) is a severe complication occurring in about 10% of monochorionic twin pregnancies. The chronic unbalanced transfusion of blood across placental vascular communications from the donor to the recipient twin may lead to impairment of various organ systems in the affected twins. In Hamburg, Germany, since 1995 patients with TTTS were treated with fetoscopic laser coagulation as the first causal therapeutic strategy. All survivors after laser surgery were followed up in the University Children's Hospital in Bonn, Germany. In this article, we summarize long-term follow-up studies from our German study population and compare our results with data from the literature.     

Increased risk of placental abruption after solomon laser treatment of twin-twin transfusion syndrome

To evaluate the relative risk of placental abruption in monochorionic (MC) twin pregnancies complicated with twin-to-twin transfusion syndrome (TTTS) and treated with endoscopic laser coagulation of placental vessels (ELCPV).A retrospective analysis from January 2004 and December 2015 of 373 TTTS pregnancies, treated with selective ELCPV until January 2012 (287 cases), after which the Solomon technique was introduced (86 cases), compared with 243 normal MC pregnancies.A significant improvement in perinatal survival was observed after the introduction of the Solomon technique when compared to the selective procedure (77% vs 54%, p < 0.001).The rate of placental abruption was 1% (3/243) in normal MC pregnancies, 6% (21/373) in TTTS group, increased with Solomon technique (12/86, 14%, vs 9/287, 3%, p < 0.001).MC twin pregnancies treated with laser coagulation of placental vascular anastomoses could be at increased risk of placental abruption, especially when the Solomon technique is used.     

Placental characteristics in monochorionic twins with and without twin anemia-polycythemia sequence

OBJECTIVE: To study the placental angioarchitecture of monochorionic placentas with and without twin anemia-polycythemia sequence. METHODS: Eligible were all placentas from monochorionic twin gestations, not complicated by twin-to-twin transfusion syndrome and resulting in double survival. The study was conducted at two European Fetal Therapy Centers between 2002 and 2008. Placental angioarchitecture was evaluated using colored dye injection. Diagnosis of twin anemia-polycythemia sequence was based on the presence of large intertwin hemoglobin difference without the degree of amniotic fluid discordance that is required for the diagnosis of twin transfusion syndrome. RESULTS: Three-hundred thirteen monochorionic twin pregnancies were eligible for the study but placental data could not be completed for 62 placentas (20%). This left 251 monochorionic twin pregnancies of which 11 (4%) fulfilled the criteria for twin anemia-polycythemia sequence. The median number of anastomoses in monochorionic placentas with and without twin anemia-polycythemia sequence was 3 (range: 2-5) and 7 (range: 0-25), respectively (P<.001). Small anastomoses were present in 91% (10/11) of twin anemia-polycythemia sequence-placentas compared with 5% (12/240) of cases without twin anemia-polycythemia sequence (P<.001). Arterioarterial anastomoses were absent in twin anemia-polycythemia sequence-placentas and present in 89% (213/240) of placentas without twin anemia-polycythemia sequence (P<.001). CONCLUSION: Monochorionic twin placentas with twin anemia-polycythemia sequence are characterized by a paucity of anastomoses and the absence of arterioarterial anastomoses. The few anastomoses that are present in twin anemia-polycythemia sequence placentas are mostly small arteriovenous anastomoses.     

Outcomes of dichorionic triplet pregnancies

OBJECTIVE: The objective of this study was to describe outcomes in a series of dichorionic triplet pregnancies. STUDY DESIGN: All triplet pregnancies evaluated in our obstetric sonography unit from 1993 to 2000 were identified. Those containing a monochorionic twin pair were included. Prenatal and neonatal records were reviewed. Statistical comparison was performed by using Wilcoxon matched-pairs signed-ranked sum test. RESULTS: Seventeen cases met inclusion criteria. Two pregnancies (11.8%) were delivered spontaneously before viability, at 22 and 21 weeks. Twin-twin transfusion syndrome was diagnosed in the second trimester in the monochorionic pair in 3 pregnancies (17.6%). In the remaining 12 pregnancies, mean gestational age at delivery was 33.5 +/- 2.3 weeks. The median birth weight of 23 neonates from individual monochorionic twin pairs was 1810 g (interquartile range, 1540-2180 g), which was significantly lower than the median birth weight of 12 triplets supplied by a separate placenta, 2125 g (interquartile range, 1762-2390 g) (P =.01). CONCLUSION: Twin-twin transfusion syndrome or spontaneous loss before viability complicated approximately 30% of dichorionic triplet pregnancies. Lower birth weights were noted in triplets from monochorionic twin pairs.     

Ultrasound in twins: Dichorionic and monochorionic

The objective of this review is to assess the evidence that supports the use of ultrasound in twin pregnancies. Although many of the indications for obstetric ultrasound are the same in both singleton and multiple gestations, there are special considerations as well as unique conditions in twins that require additional imaging studies. The reasons for ultrasound in twins include pregnancy dating, determination of chorionicity, nuchal translucency assessment, anatomical survey, placental evaluation, cervical length assessment, routine fetal growth, and serial surveillance of pregnancies complicated by anomalies, cervical shortening, fetal growth disturbances, and amniotic fluid abnormalities. Twins with monochorionic placentation require heightened scrutiny for monoamnionicity, conjoined twins, twin reversed arterial perfusion (TRAP) syndrome, twin–twin transfusion syndrome, unequal placental sharing with discordant twin growth or selective intrauterine fetal growth restriction (IUGR), twin anemia–polycythemia sequence (TAPS), and single fetal demise. Ultrasound is essential for the detection and management of conditions that can complicate dichorionic and monochorionic twin pregnancies.     

What fetal medicine specialists should know about the monochorionic placenta

Monochorionic twins are at risk of transfusion imbalances as long as they are connected to the shared placenta during their intrauterine journey. This review article addresses the macroscopic examination of the monochorionic placenta at the time of birth and explains placental dye injection studies to document the vascular anastomoses and placental sharing. We elaborate on the different types of anastomoses, the importance of how the placenta is divided between the twins, and the angioarchitecture in twin-twin transfusion syndrome, twin anemia polycythemia sequence and selective fetal growth restriction.     

Late onset of discordant growth in a monochorionic twin pregnancy: vascular anastomoses determine fetal growth pattern and not placental sharing

Twin-twin transfusion syndrome in monochorionic twin pregnancies has a complex and variable clinical presentation. We present the first documented case where two unidirectional arteriovenous anastomoses connecting the donor twin's larger with the recipient's smaller placental part produce late onset of discordant growth and subsequent twin-twin transfusion syndrome. We conclude that the haemodynamic effects of the anastomoses caused the observed discordant fetal development and not the unequally shared placenta.     

Virtual three-dimensional placentoscopy: a new approach to assess residual anastomoses following laser photocoagulation in twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome (TTTS) complicates 10% of monochorionic twin pregnancies and it is consequence of an unbalanced exchange blood through the vascular anastomoses at placental surface. If not treated, mortality rates in TTTS may be as high as 80–100%. Laser photocoagulation of the placental anastomoses is the first treatment option; however, in some situations, the damage of the placenta in the postpartum may become difficult the residual anastomoses identification. We propose a new non-invasive technique to assess the residual anastomoses using computed tomography (CT) scan data to generate a three-dimensional (3D) virtual placentoscopy.