The twin transfusion syndrome. Clinical observations on 35 affected pairs

Fetal and Neonatal Circulatory Disorders in Twin to Twin Transfusion Syndrome (The Secondary Publication)

Twin to twin transfusion syndrome (TTTS) is a major complication of monochorionic diamniotic (MD) twins, and its onset is known to be associated with placental vascular anastomoses and blood flow imbalance. In a typical case of TTTS, the recipient develops polyhydramnios, weight gain, cardiomegaly and hydrops fetalis in the uterus. In contrast, the donor develops oligohydramnios and intrauterine growth restriction. Recently, the significance of the renin-angiotensin-aldosterone system (RAAS) that transfers from the donor to the recipient has attracted interest in the fetal circulation of TTTS. The donor has decreased renal blood flow due to decreased circulating blood volume. For this reason, the secretion of RAAS hormones is augmented in the fetal kidneys of the donor. In TTTS, these RAAS hormones from the donor transfer to the recipient through the anastomosed vessels. In addition to excess preload, the recipient heart is exposed to excess afterload due to systemic vasoconstriction through RAAS hormones. Commonly occurring complications in the recipient include myocardial hypertrophy, atrioventricular valve regurgitation, and pulmonary valve stenosis or pulmonary atresia. Fetoscopic laser photocoagulation (FLP) has been introduced recently because neither mortality nor neurological morbidity have been satisfactorily improved with conventional treatment. FLP is a curative method that may improve the prognosis of TTTS. In Japan, this procedure has been performed frequently, and positive neurological outcomes have been achieved.

Fetal stroke and cerebrovascular disease: Advances in understanding from lenticulostriate and venous imaging, alloimmune thrombocytopaenia and monochorionic twins

Fetal stroke is an important cause of cerebral palsy but is difficult to diagnose unless imaging is undertaken in pregnancies at risk because of known maternal or fetal disorders. Fetal ultrasound or magnetic resonance imaging may show haemorrhage or ischaemic lesions including multicystic encephalomalacia and focal porencephaly. Serial imaging has shown the development of malformations including schizencephaly and polymicrogyra after ischaemic and haemorrhagic stroke. Recognised causes of haemorrhagic fetal stroke include alloimmune and autoimmune thrombocytopaenia, maternal and fetal clotting disorders and trauma but these are relatively rare. It is likely that a significant proportion of periventricular and intraventricular haemorrhages are of venous origin. Recent evidence highlights the importance of arterial endothelial dysfunction, rather than thrombocytopaenia, in the intraparenchymal haemorrhage of alloimmune thrombocytopaenia. In the context of placental anastomoses, monochorionic diamniotic twins are at risk of twin twin transfusion syndrome (TTTS), or partial forms including Twin Oligohydramnios Polyhydramnios Sequence (TOPS), differences in estimated weight (selective Intrauterine growth Retardation; sIUGR), or in fetal haemoglobin (Twin Anaemia Polycythaemia Sequence; TAPS). There is a very wide range of ischaemic and haemorrhagic injury in a focal as well as a global distribution. Acute twin twin transfusion may account for intraventricular haemorrhage in recipients and periventricular leukomalacia in donors but there are additional risk factors for focal embolism and cerebrovascular disease. The recipient has circulatory overload, with effects on systemic and pulmonary circulations which probably lead to systemic and pulmonary hypertension and even right ventricular outflow tract obstruction as well as the polycythaemia which is a risk factor for thrombosis and vasculopathy. The donor is hypovolaemic and has a reticulocytosis in response to the anaemia while maternal hypertension and diabetes may influence stroke risk. Understanding of the mechanisms, including the role of vasculopathy, in well studied conditions such as alloimmune thrombocytopaenia and monochorionic diamniotic twinning may lead to reduction of the burden of antenatally sustained cerebral palsy.

Hematological disorders at birth in complicated monochorionic twins

INTRODUCTION

Monochorionic twins are at risk of severe complications including twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS) and acute peripartum TTTS. The pathophysiology is based on inter-twin blood transfusion through placental vascular anastomoses. Areas covered: This review focuses on the incidence, management and outcome of neonatal hematological complications at birth in TTTS, TAPS and acute peripartum TTTS. Expert commentary: Hematological disorders are often present at birth in monochorionic twins and include acute or chronic anemia, polycythemia and thrombocytopenia. Routine measurement of complete blood counts in all complicated monochorionic twins is strongly recommended. Increased awareness on these disorders and correct diagnostic tests will lead to prompt and adequate management at birth.

Twin-to-Twin Transfusion Syndrome: Definition, Staging, and Ultrasound Assessment

Objective: The purpose of this article is to review the definition of twin-to-twin transfusion syndrome (TTTS) and the sonographic diagnostic assessment of these cases prior to therapy.

Materials and Methods: The article addresses the terminology used to refer to the condition and describes the systematic ultrasound assessment of the condition, including the ultrasound diagnosis, the staging of the disease, cervical assessment and pre-operative mapping.

Results: From an etymologic and medical point of view, the term ‘fetofetal transfusion’ is more appropriate than ‘TTTS’. However, as the latter, and its attendant acronym TTTS, have been widely adopted in the English language, it is impractical to change at this point. TTTS is defined sonographically in the combined presence of a maximum vertical pocket (MVP) of 8 cm or greater in one sac and 2 cm or less in the other sac, regardless of the gestational age at diagnosis. Staging of the condition using the Quintero staging system is practical, reproducible, and accepted. Transvaginal cervical length assessment should be an integral part of the ultrasound evaluation. Pre-operative mapping to anticipate the location of the placental vascular anastomoses and avoid injuring the dividing membrane is also discussed.

Conclusions: The term ‘TTTS’ can continue to be used in the English medical literature. The condition can be diagnosed and assessed following a systematic ultrasound methodology. The use of such ultrasound methodology breaks the examination into a distinct set of components, assuring a comprehensive examination and proper communication among caregivers.

Management of severe twin to twin transfusion syndrome

In monozygotic twin pregnancies embryonic splitting within three days of fertilisation, which occurs in approximately one-third of cases, results in two separate fetuses with independent placental circulations. Splitting after the third day of fertilisation is associated with vascular communications between the placentae; when cleavage is delayed beyond day 12 the fetuses are conjoint. In some monochorionic twin pregnancies imbalance in the net flow of blood across the placental vascular communications from one fetus (the donor) to the other (the recipient) results in twin to twin transfusion syndrome (TTS).

Is there increased monozygotic twinning after assisted reproductive technology?

Over the past two decades there has been an association between assisted reproductive technologies and increased monozygotic twinning. The association is not clear nor are the causes of assisted reproductive technology-related monozygotic twinning understood, although there are several theories as to the possible mechanisms involved. This review looks at some of the assisted reproductive technologies which may be associated with an increased risk of monozygotic twinning such as intracytoplasmic sperm injection, assisted hatching and blastocyst transfers. Determining the true incidence of monozygotic twinning after assisted reproductive technologies is important as there is a well-documented increase in perinatal morbidity and mortality of monozygotic twins compared to singleton and dizygotic pregnancies.

Exploiting human anatomical variability as a link between genome and cognome

Although talents and disabilities appear to run in families, direct links between genes and cognitive ability are difficult to establish. Investigators are currently searching for intermediate phenotypes with plausible links to both genome and cognome (the cognitive phenotype). Cortical anatomy could provide one such intermediate phenotype. Variation in cortical size, asymmetry and sulcal pattern is influenced by genetic variation in neurotrophic factors and can predict variation in verbal and mathematical talent. Anecdotal evidence suggests that individuals with a rare morphological variant of Sylvian fissure sometimes have superior visualization ability combined with verbal deficits. Documentation of such 'cognitive cortical syndromes' might prove as genetically informative as the identification of dysmorphic syndromes associated with mental retardation. A necessary prerequisite for the establishment of such syndromes is a reliable technique for the identification of cortical patterns. Recent technical advances in software for automatically labeling and measuring cortical sulci now provide the possibility of establishing standard measures for their shape, size and location. Such measures are a prerequisite for genetic studies of cortical patterns that could illuminate the neurodevelopmental pathways by which genes affect cognitive ability.

Haemoglobin differences at birth in monochorionic twins without chronic twin-to-twin transfusion syndrome

OBJECTIVES

To determine the haemoglobin (Hb) differences at birth in monochorionic (MC) twins without chronic twin-to-twin transfusion syndrome (TTTS) in relation to birth order and placental vascular anatomy.

METHODS

All consecutive cases of MC twins without chronic TTTS and dichorionic (DC) twins delivered at our centre and admitted to our neonatal nursery between June 2002 and December 2004 were included in our study. We analysed Hb differences at birth and on day 2, in relation to birth order and placental vascular anatomy.

RESULTS

Forty-five pairs of MC twins and 71 pairs of DC twins were included. Mean Hb differences at birth in MC and DC twins were similar, respectively 1.5 and 1.4 g/dL. Hb differences >5 g/dL at birth were found in 2% (1/45) of MC twins compared to 8% (6/71) in DC twins. On day 2, mean Hb differences in MC twins increased to 3.8 g/dL, and the rate of MC twins with Hb differences >5 g/dL increased to 27% (12/45) (p < 0.001). Mean Hb differences and the percentage of twins with Hb differences >5 g/dL in DC twins did not change on day 2. In MC twins, Hb levels measured on day 2 were significantly higher in second-born twins than in first-born twins, respectively 17.7 and 15.5 g/dL (p = 0.002). Hb differences on day 2 were significantly higher in MC twins with superficial vascular anastomoses than those without superficial anastomoses, respectively 4.0 g/dL and 1.5 g/dL (p = 0.036).

CONCLUSIONS

Hb differences occur more frequently in MC twins without chronic TTTS than in DC twins, but only when measured on the second day of life. Hb differences in MC twins are associated with birth order and superficial vascular anastomoses.

Anemia in the newborn

In neonatal period anemia is a complex problem owing to the unique blood picture. The erythrocytic system undergoes serial adaptation to meet progressively changing demands of oxygen in the embryo, the fetus and neonate. This leads to rapid change in normal hematological change in post-birth period. Definition of anemia is difficult because as described earlier, several important factors influence normal blood in the newborn infants. The etiology of neonatal anemia can be classified into i) hemorrhage (ii) hemolysis (iii) failure of red cell production. Severe fetal hemorrhage may accompany various placental anomalies like placenta praevia, abruptio placenta and accidental incision of placenta during the caesarian section. It is reported that 10% of all infants born following placenta praevia and 4% of infants born following abruptio placenta present with severe anemia. The passage of fetal erythrocytes in maternal circulation occurs commonly during pregnancy. In 50% of pregnancies some fetal cells are passed in maternal circulation sometimes during gestation or during birth process. Treatment of a neonate with anemia due to blood depends on the degree of hypovolemia or anemia and whether the blood loss has been acute or chronic. Newborn with pale skin should be differentiated from an asphyxiated baby.

Twin-twin transfusion syndrome

The understanding and management of twin-twin transfusion syndrome has evolved significantly over the past few years. Improved and standardized sonographic diagnostic criteria, understanding of the heterogeneic nature of the syndrome, development of an anatomical and reproducible surgical technique for the identification of vascular anastomoses, and technological advances and developments now allow clinicians to view the disease as a more readily understandable and treatable condition. Many tasks remain, including education of peers, better screening and diagnosis, and further development of surgical instruments. Generalization of treatment outcomes should no longer apply given the varied results with disease stage. Confirmation of our tailored approach to management of the disease according to stage should soon be corroborated with an appropriate clinical trial.

The treatment of twin-twin transfusion syndrome

The twin-twin transfusion syndrome (TTTS) is the most common serious complication of monochorionic twin gestations, affecting between 4% and 35% of monochorionic twin pregnancies each year in the United States. The TTTS accounts for 17% of all perinatal mortality associated with twin gestations. Standard therapy in the United States has most commonly been serial amnioreduction, which appears to improve the overall outcome. Intertwin microseptostomy similarly improves outcome but has no survival advantage over serial amnioreduction. Survivors of TTTS treated by serial amnioreduction have an 18% to 26% incidence of sonographically detectable brain abnormalities. Selective fetoscopic laser photocoagulation of chorioangiopagus has emerged as an alternative treatment strategy in TTTS with at least comparable if not superior survival to serial amnioreduction. The superiority of fetoscopic laser treatment of TTTS remains unproven and is the subject of a National Institutes of Health (NIH)-sponsored prospective randomized clinical trial comparing aggressive serial amnioreduction with selective fetoscopic laser photocoagulation for severe TTTS.

The epigenesis of planum temporale asymmetry in twins

Variation in hemispheric asymmetry of the planum temporale (PT) has been related to verbal ability. The degree to which genetic and environmental factors mediate PT asymmetry is not known. This study examined the heritability for planar asymmetry in 12 dizygotic (DZ) and 27 monozygotic (MZ) male twin pairs who were between 6 and 16 years of age. There was weak but positive evidence for heritability of planar asymmetry. Co-twin similarity for planar asymmetry and Sylvian fissure morphology increased when excluding twins discordant for writing hand and when excluding twins exhibiting birth weight differences >20% from the analyses. Birth weight differences were also related to twin differences in total cerebral volume, but not central sulcus asymmetry. These results suggest that exogenous perinatal factors affect the epigenesis of planar asymmetry development.

Determinação dos valores hematológicos e das concentrações séricas de ferro e ferritina em sangue de cordão umbilical de recém-nascidos de termo e pré-termo no Hospital Israelita Albert Einstein de São Paulo

Determinaram-se os valores hematológicos (Hb, Ht, VCM, HCM, CHCM, reticulócitos) e as concentrações séricas de ferro e ferritina no sangue de cordão umbilical de recém-nascidos (RN) no Hospital Albert Einstein. A amostra continha 32 RN de termo (T) e 30 RN pré-termo (PT). Os RN apresentavam-se clinicamente sadios, sendo excluídos os que apresentaram intercorrências clínicas ou no momento do parto. O sangue foi colhido por punção da veia umbilical até 5 minutos após a dequitação e encaminhado ao laboratório de patologia clínica para processamento laboratorial. Os valores hematológicos encontram-se mais elevados no grupo de RNT em relação ao grupo de RNPT (p<0,05). Ajustando-se um modelo de regressão logística múltipla, o Ht tem valor preditivo para a prematuridade, observando-se uma relação inversamente proporcional entre o valor do Ht e a idade gestacional.

Ultrasound in the diagnosis of twin-to-twin transfusion syndrome--a preliminary report

OBJECTIVE

The aim of this study was to show the diagnostic possibilities of ultrasound in twin-to-twin transfusion syndrome (TTTS), to demonstrate its usefulness in cases of hemoglobin difference < 5 g/dL in neonates as well as in cases complicated by intrauterine death of one or both twins.

STUDY DESIGN

The study included 4 pairs of twins. In two cases 3 fetuses died in utero. In the other two the hemoglobin difference in newborn infants was < 5 g/dL. The ultrasound examination, evaluating the fetal anatomy and biometry, amniotic fluid volume, placentation, was performed. The special attention was paid to polyhydramnios/oligohydramnios, discordant fetal growth (fetal weight, abdominal circumference), the presence of fetal hydrops, ascites, pericardial effusion. Doppler blood flow velocimetry has been done in umbilical vessels, middle cerebral artery. The data was compared with normal reference values for singleton pregnancies. The waveforms from both uterine arteries were also evaluated to exclude placental insufficiency. Additionally the blood flow through the AV valves was measured to exclude or confirm its regurgitation. Postnatally the hemoglobin difference was evaluated if available and compared with sonographic findings.

RESULTS

In all cases inter-twin difference in abdominal circumference was greater than 18 mm and inter-twin weight difference of more than 15%. We observed polyhydramnios/oligohydramnios in all twin pregnancies. It has been found decreased PI in middle cerebral artery in larger fetus (recipient) in all our cases (comparing to single pregnancy). PI values for this vessel in smaller fetuses were within normal range (for single pregnancy). PI values in umbilical arteries of recipients were abnormal (increased PI or absent end-diastolic flow).

COMMENTS

The sonographic criteria seem to be very useful in diagnosis of twin-to-twin transfusion syndrome, especially in cases where the measurement of hemoglobin level is impossible. Doppler blood flow velocimetry in fetal vessels helps to explain the changes in fetal hemodynamics in TTTS.

Twin-twin transfusion syndrome: the challenge of etiology-based management decisions

Studies published in the past year have attempted to model the pathophysiology of the twin-twin transfusion syndrome and also to establish the minimal diagnostic criteria for the condition. Many papers focused on treatment regimens and their sequelae. Aggressive treatment with serial amnioreduction continues to predominate, and appears to be more successful than conservative medical management, whereas selective feticide is reserved for cases that fail to respond to amnioreduction. Small series utilizing laser ablation and amniotic septostomy appeared; with laser proponents suggesting that their approach may carry a lower risk of neurological sequelae. Progress in ultrasound and Doppler techniques has begun to yield earlier and better diagnostic approaches which, coupled with an awareness of the possible anastomotic configurations, may allow for the selection of the management protocol most likely to succeed in each individual case.

Anemia in newborn

Various blood indices vary in a newborn as compared to older child or adult. It depends on the gestational age, day of life, maternal factors, mode of delivery and site of blood collection. Hemoglobin, HCT & MCV tend to be higher in newborns. They further increase in first 2 days of life. Reticulocytosis and presence of nucleated red cells are normally seen in first week of life. Neonatal anemia is a common problem in NICU. It is usually caused by either hemorrhage or hemolysis and rarely due to decreased production. Hemorrhage can be ante or intra or post natal and it could be external or internal. It could be acute or chronic. Management of acute severe hemorrhage includes packed cell transfusion. Hemolysis is usually due to isoimmune hemolysis, G6PD deficiency or rarely due to the hemoglobinopathy like alpha-thalassemia or due to spherocytosis. Usually patients will have indirect hyperbilirubinemia which needs phototherapy or exchange transfusion. Rarely congenital pure red cell aplasia can present at birth with physical anomalies and anemia. Treatment of neonatal anemia depends on the arteriology.

The consequences of monochorionic placentation

Monochorionic (MC) placentation occurs in two-thirds of monozygous twins and approximately 0.3% of all spontaneous conceptions. Vascular anastomoses within the placenta allow intertwin transfusion to occur, which is in most cases a normal event. However, imbalance in this flow may lead to the clinical sequelae observed, with acute, chronic or reverse intertwin transfusion. Acute transfusion describes the events following the death of one of an MC twin pair in utero, with an approximately 1 in 4 chance of demise or neurological damage in the co-twin. Chronic intertwin transfusion, otherwise termed feto-fetal transfusion syndrome, arises following the gradual flux of blood from one twin (the donor) to its sibling fetus (the recipient). The ensuing polyhydramnios places the pregnancy at risk of preterm amniorrhexis and/or labour, notwithstanding the specific sequelae seen in these fetuses following chronic in utero insult. Reverse transfusion describes the most bizarre form of intertwin transfusion: acardiac twinning. Retrograde perfusion of one of the twins with deoxygenated blood leads to the formation of a non-viable acardiac parasite and a 'pump twin' struggling to maintain the cardiac output required to perfuse both twins.

The aetiology and management of twin-twin transfusion syndrome

Twin-to-twin transfusion syndrome presents in the mid-trimester with gross discordance in amniotic fluid volume, and complicates 10-15 per cent of monochorionic twins. Recent studies suggest a primary vascular basis in which a paucity of the bidirectional superficial anastomoses normally found in monochorionic twins is unable to compensate for haemodynamic imbalance resulting from unidirectional transfusion along deeper arterio-venous anastomoses. It is associated with high rates of perinatal mortality from ruptured membranes, hydrops and growth restriction, and a significant morbidity from cardiac and neurological sequelae in particular. Serial aggressive amnioreduction is the current treatment of choice, with survival in around two thirds of cases. In the remaining third, with features suggesting a poor outcome, selective fetocide may have a role. Current attempts at vascular ablative therapies have been associated with inferior survival rates, but the long term therapeutic goal remains the identification and ablation of the shared chorionic vasculature.

Neonatal neurologic characteristics of preterm twin infants <1,250 gm birth weight

The study objectives were to determine the incidence, time of onset, and clinical characteristics of neonatal neurologic injury in preterm twin infants <1,250 gm birth weight. Forty-one twin infants of birth weight 929 gm +/- 160 and 27.3 +/- 1.96 weeks gestation were evaluated and compared to 225 singleton infants <1,250 gm. Seventeen infants were monozygotic and 24 dizygotic. Six of the 9 monozygotic pregnancies were complicated by the polyhydramnios/oligohydramnios syndrome; a weight discordancy of >20% was observed in 8 of the monozygotic twin sets and polycythemia (hematocrit >65%) in 3 infants. Nine (22%) of the 41 infants died. Periventricular-intraventricular hemorrhage (PV-IVH) developed in 11 (27%) of 41 infants and was severe in 9 (22%) infants. IVH was noted on day 1 (n = 2), day 2 (n = 3), and day 3 (n = 6). IVH developed in 69 (30%) of the 225 singletons and was severe in 28 (12%) infants. Twin infants were more likely to have been delivered via cesarean section, to have required intubation in the delivery room, and to have been administered surfactant as compared with singletons (P < .01). It was concluded that preterm twin infants <1,250 gm are at high risk for developing severe IVH, and that the onset of IVH was within the first 3 postnatal days in all cases.

The hidden mortality of monochorionic twin pregnancies

In an ultrasound screening study at 10 to 14 weeks of gestation for measurement of fetal nuchal translucency thickness there were 102 monochorionic and 365 dichorionic twin pregnancies. In the monochorionic compared with the dichorionic pregnancies there was a higher rate of fetal loss before 24 weeks of gestation (12.2% versus 1.8%), perinatal mortality (2.8% versus 1.6%), prevalence of delivery before 32 weeks (9.2% versus 5.5%), and prevalence of birthweight below the 5th centile in both twins (7.5% versus 1.7%). However, the proportion of pregnancies with a birthweight discordancy of more than 25% was similar in the two groups (11.3% versus 12.1%).

Potential value of fetal echocardiography in the differential diagnosis of twin pregnancy with presence of polyhydramnios-oligohydramnios syndrome

OBJECTIVE

Our purpose was to establish whether index values of cardiac performance could discriminate between the twin-twin transfusion syndrome and placental insufficiency as the etiology of the polyhydramnios-oligohydramnios sequence in monochorionic diamniotic twins.

STUDY DESIGN

Thirteen monochorionic diamniotic twin pregnancies with ultrasonographic evidence of polyhydramnios-oligohydramnios sequence had a complete echocardiography. The etiology was confirmed postnatally: placental insufficiency in eight pairs and the twin-twin transfusion syndrome in five. Intertwin comparisons were made for the following cardiac parameters: cardiothoracic index, end-diastolic thickness of the ventricular walls and septum, aortic and pulmonary artery Doppler peak velocities, ejection and acceleration times, left ventricular shortening fraction, and combined cardiac output and output indexed to fetal weight.

RESULTS

All five recipient twins had thickened ventricular walls. The left ventricular shortening fractions and outputs were significantly increased in the donor twin with twin-twin transfusion syndrome and normal in placental insufficiency.

CONCLUSION

In twin-twin transfusion syndrome the donor twin shows evidence of a hyperdynamic cardiac state. Intertwin comparison of cardiac parameters, especially the left ventricular shortening fraction, can be considered a useful tool in diagnosing the different etiologies of the polyhydramnios-oligohydraminos sequence.

Morbidity and mortality of discordant twins up to 34 weeks of gestational age

The combination of weight discordance and prematurity implies a high perinatal morbidity and mortality for the affected twins. Several pathomechanisms may be responsible for the weight difference in twins including a different genetic growth potential in dizygotic twins, placenta insufficiency in one twin, and chronic feto-fetal transfusion (CFFT). Little is known about neonatal morbidity and mortality of discordant twins. Therefore, a retrospective, case-controlled study on preterm discordant twins up to 34 weeks gestation was carried out. Twenty-seven (27,3%) of 99 twin pairs born in our clinic had a birth weight difference of more than 20%. The control group consisted of 27 non-discordant twins matched for gestational age. Discordant twins showed a significantly higher mortality (19%) than the control twins (2%). Severe intracranial haemorrhage (ICH) and persistent ductus arteriosus Botalli (PDA) were found more often in discordant twins than in the control group. The increased mortality and morbidity of discordant twins compared with concordant twins matched for gestational age indicates that the increased morbidity and mortality of preterm weight discordant twins is not only due to prematurity, but is also related to the discordance itself. Thirteen (48.1%) of the weight discordant twin pairs fulfilled the criteria for CFFT. Twins with CFFT differed significantly from controls with respect to the incidence of mortality and the rate of severe ICH, PDA, and the necessity of postnatal cardiopulmonary resuscitation. By contrast, no significant differences were found between discordant twins without CFFT and controls. Thus, CFFT appears to be a major contributing factor for increased mortality and morbidity of weight discordant twins. Intra-twin pair analysis revealed a higher rate of postnatal hypoglycaemia in the smaller twins only, probably caused by insufficient glycogen storage due to intra-uterine malnutrition. Mortality was the same for both the larger and the smaller twins. It may be concluded that neonatal outcome of smaller twins who have survived intra-uterine malnutrition is the same as in larger twins. Intra-twin pair analysis in twins with CFFT revealed no significant differences except for a higher rate of ICH grade 2-4 in the larger twins which might be explained by hypervolaemia of the recipient.

CONCLUSION

Morbidity and mortality of weight discordant twins are increased. CFFT appears to be a major contributing factor for the increased mortality and morbidity. Postnatal mortality was the same in acceptor and donor; however, the acceptor had a higher postnatal morbidity.

Syndromes in twins

There is a higher incidence of perinatal mortality and morbidity in twins than in singleton pregnancies. The main reason for this increase is the higher incidence of preterm delivery in twins. There are special conditions unique to twins that also contribute to this increased perinatal morbidity and mortality. These conditions include monoamniotic twins, congenital anomalies unique to twins, ie, conjoined twins and acardia, intrauterine fetal demise, and twin-to-twin transfusion syndrome. These conditions are the subject of this review. The prenatal determination of chorionicity is discussed first, because this assessment is key to the diagnosis and management of many of these conditions.

Intrapair differences in personality and cognitive ability among young monozygotic twins distinguished by chorion type

We evaluated placentation effects on behavioral resemblance of 44 pairs of monozygotic (MZ) twin children. Tested at ages 4-6, the twins' zygosity and placental type had been determined at their delivery. The sample included 23 monochorionic (MC) and 21 dichorionic (DC) MZ twin pairs: DC-MZ twins result from separation of blastomeres within 72 h of ovulation; MC-MZ twins arise from later duplication of the inner cell mass. Twins were individually administered the McCarthy Scales of Cognitive Ability, while their mothers separately rated each cotwin on an individualized 280-item form of the Personality Inventory for Children (PIC). Absolute differences between MC-MZ cotwins were smaller than those between DC-MZ cotwins for all 20 PIC scales, significantly so for 3 of 4 factor scales, 8 of 12 clinical scales, and 2 of 4 validity/screening scales from the PIC; in contrast, no consistent differences in intrapair resemblance of mono- and dichorionic MZ twins were found for the McCarthy Scales. The chorion differences found in the PIC data cannot be due to genetic differences, because all pairs are monozygotes; nor are they associated with differences in parity, gestational age, birth weight, maternal education, palmar dermatoglyphic asymmetry, or maternal knowledge of chorion type. We interpret our findings as suggestive evidence that variation in timing of embryological division, with effects on MZ twins' placental vasculature, has significant consequences for some dimensions of their behavioral development, as well.

Angioarchitecture of monochorionic placentas in relation to the twin-twin transfusion syndrome

OBJECTIVE

Twin-twin transfusion syndrome in the midtrimester is associated with a perinatal mortality rate exceeding 80%. Although attributed to intertwin transfusion along vascular anastomoses, these occur in all monochorial placentas, not just the 10% with twin-twin transfusion syndrome. We compared fetoplacental angioarchitecture in monochorionic twin placentas with and without twin-twin transfusion syndrome.

STUDY DESIGN

The fetoplacental circulations of both twins in 20 monochorial placentas were perfused immediately after delivery under optimal physiologic conditions and anastomoses delineated by dye-contrast injection. Ten were from pregnancies with evidence of midtrimester twin-twin transfusion syndrome and 10 were from pregnancies without twin-twin transfusion syndrome.

RESULTS

Placentas from pregnancies with twin-twin transfusion syndrome had significantly fewer anastomoses than did those without twin-twin transfusion syndrome, both overall (median one versus six, respectively; p < 0.001) and for each of the different types (arterioarterial, venovenous, and arteriovenous, p < 0.001). Whereas multiple anastomoses were present in all controls, only one twin-twin transfusion syndrome placenta had more than a single communication. Anastomoses in the twin-twin transfusion syndrome group were more likely to be of the deep than the superficial type (80% vs 36% in controls, p < 0.01).

CONCLUSIONS

Placental vascular anastomoses in monochorial pregnancies complicated by twin-twin transfusion syndrome are both fewer in number and of a different type than those without twin-twin transfusion syndrome. These differences seem implicated in the underlying pathophysiologic features of twin-twin transfusion syndrome and are of relevance to the development of newer therapies such as placental laser surgery.

Severe twin-twin transfusion syndrome: current management concepts

The presence of functioning vascular anastomoses within the monochorionic placentation of a monozygotic twin pregnancy is responsible for the twin-twin transfusion syndrome. This is a heterogeneous disorder with a wide spectrum of severity. In the most severe form it results in the oligohydramnios-polyhydramnios sequence with a marked disparity in intertwin biometry and amniotic fluid volume. Without therapy, the perinatal mortality of severe twin-twin transfusion syndrome is 60-100%. Several therapeutic interventions have been attempted with therapeutic amniocentesis producing the most consistent improvement in fetal survival rates. The outcome of 10 cases of severe twin-twin transfusion syndrome, presenting as the oligohydramnios-polyhydramnios sequence, is presented. Gestational age at presentation ranged from 20-34 weeks. Three fetuses were hydropic at initial presentation and of these only 1 survived. All cases were treated with serial aggressive therapeutic amniocentesis, the number of procedures ranging from 1-9/patient. The volume of amniotic fluid removed ranged from 3,200-14,000 mL. Gestation was prolonged a mean of 46 days (range 1-106 days). The perinatal survival rate was 65% (13/20 infants). Preterm premature rupture of membranes and secondary preterm birth complicated 1 pregnancy treated with therapeutic amniocentesis. Short-term morbidity in the liveborn infants was predominantly secondary to prematurity and renal cortical necrosis. Severe twin-twin transfusion syndrome is the most common aetiology of the oligohydramnios-polyhydramnios sequence. Therapeutic amniocentesis offers an intervention that may reduce the high perinatal loss rate previously observed with this disorder.

The value of Doppler ultrasound in the diagnosis and management of twin-to-twin transfusion syndrome

To evaluate the efficiency of the Doppler examination of umbilical arterial blood flow for the antenatal diagnosis and the monitoring of fetal condition during intrauterine treatment of twin-to-twin transfusion syndrome (TTTS), we studied 33 pairs of twins including 5 TTTS cases. In all cases umbilical arterial blood flow was examined by Doppler ultrasound and pulsatility index (PI) was calculated as umbilical arterial impedance. In twins with TTTS, PI of the recipient was outside the normal range and the difference of PI was greater than +0.5. In discordant twins without TTTS and concordant twins, the PI was within the normal range and the difference of PI ranged from -0.5 to +0.5. In 2 cases these findings were found before the appearance of fetal hydrops. In 2 TTTS cases transmaternal digitalization prevented the development of hydrops in the recipient. The difference of PI decreased with improvement in the fetal condition, and vice versa. Our data suggested that, in cases with TTTS, Doppler examination of umbilical arterial blood flow was effective in predicting fetal hydrops. Doppler was also very useful for monitoring the fetal condition during intrauterine treatment.

Twin-to-twin transfusion syndrome: a subset of the twin oligohydramnios-polyhydramnios sequence

OBJECTIVE

Our purpose was to assess the adequacy of currently accepted criteria for the diagnosis of twin-to-twin transfusion syndrome.

STUDY DESIGN

Between April 1991 and February 1992 nine consecutive women with twin gestations and ultrasonographic findings of marked growth discordance, coexistent oligohydramnios-polyhydramnios, monochorionic placenta, and same sex of the fetus in the second trimester were evaluated. Mean gestational age at diagnosis was 19 weeks 5 days +/- 5 weeks, and mean growth discordance was 34% +/- 9%. Seven women underwent attempted sequential amniocentesis and cordocentesis at 23 weeks 6 days +/- 2 weeks 4 days to obtain amniotic fluid and cord blood from each fetus. Type O negative, leucocyte-poor, washed adult red blood cells were transfused into the small, oligohydramnic twin during cordocentesis; immediately afterward blood from the polyhydramnic twin was tested with the Kleihauer-Betke stain.

RESULTS

The combined procedure was successful in six (86%) of the cases attempted. True twin-to-twin transfusion was confirmed in only four (44%) of those initially identified by ultrasonographic criteria. Hemoglobin difference > 5 g/dl was present in only one of the four cases, and in this case the recipient was anemic.

CONCLUSIONS

Currently accepted criteria are insufficient for the diagnosis of true twin-to-twin transfusion. Ultrasonographic findings of marked growth discordance, coexistent oligohydramnios-polyhydramnios, monochorionic placenta, and same sex identify the twin oligohydramnios-polyhydramnios sequence.

Ultrasonography and Doppler studies in twin-to-twin transfusion syndrome

In 40 twin pregnancies, the evaluation of hemodynamics by ultrasound was performed during the period January 1986 through September 1991. The blood flow velocities' waveforms in the umbilical artery, umbilical vein and tricuspid valve, and the total cardiac dimension, were obtained by ultrasonography in conjunction with 3.5 MHz pulsed Doppler ultrasound. Six patients with twin pregnancies were identified as having twin-to-twin transfusion syndrome (TTS), on the basis of like-sex twins with monochorionic diamniotic placentation, vascular anastomosis in the placenta, and umbilical cord venous blood hemoglobin difference exceeding 5 g/dl at delivery. No distinctive findings for TTS were revealed by the measurement of umbilical artery blood flow velocity waveforms. However, cardiomegaly in 5 recipient fetuses and tricuspid regurgitation and biphasic umbilical vein waveforms in 3 recipient fetuses constituted characteristic features of TTS. Ultrasonography and a Doppler study might be beneficial in diagnosing TTS and evaluating the hemodynamics in a recipient fetus.

Optic nerve hypoplasia, encephalopathy, and neurodevelopmental handicap

Abnormalities of the central nervous system are frequently described in optic nerve hypoplasia. In a longitudinal study of 46 consecutive children (32 term, 14 preterm) with bilateral optic nerve hypoplasia 32 (69.5%) had associated neurodevelopmental handicap. Of these, 90% had structural central nervous system abnormalities on computed tomographic brain scans. Neurodevelopmental handicap occurred in 62.5% of the term and 86% of the preterm infants respectively. Term infants had a greater incidence of ventral developmental midline defects and proportionately fewer maternal and/or neonatal complications throughout pregnancy, while encephaloclastic lesions were commoner among the premature infants. An association of optic nerve hypoplasia with the twin transfusion syndrome and prenatal vascular encephalopathies is described.

Twin-twin transfusion syndrome

Twin-twin transfusion syndrome associated with acute polyhydramnios in one sac and severe oligohydramnios in the other, which characteristically is diagnosed between 18 and 28 weeks, is associated with a high mortality rate for the involved twins. Patients who are managed without intervention have essentially 100% perinatal mortality. Nineteen patients with this diagnosis were treated at Good Samaritan Medical Center over a 5-year period. Because of the known perinatal mortality and because of early experiences with the twin-twin transfusion syndrome, we began to actively intervene in such patients with various modes of therapy. As experience was gained, it was found that repeated therapeutic amniocenteses, if performed before severe maternal abdominal distention or labor, appears to be beneficial.

Fetofetal transfusion syndrome: do the neonatal criteria apply in utero?

Thirteen fetuses (five twin, one triplet) were compromised by fetofetal transfusion syndrome in six pregnancies, five in the mid trimester, and one in the third trimester. This diagnosis, which was suspected because of ultrasound findings of discordant growth, discordant amniotic fluid volumes, concordant external genitalia, and monochorial placentation, was confirmed postnatally in each. Nine fetuses underwent blood sampling to aid diagnosis and assessment of fetal wellbeing. In contrast to fetofetal transfusion syndrome investigated postnatally, a difference in haemoglobin concentration of 50 g/l or more in utero was found in only one pregnancy, which was near term, although all had fetal erythroblastaemia and a difference in weight of 20% or more. In vivo confirmation of shared circulation was achieved in two pregnancies by transfusing adult Rh negative red cells into the smaller fetus and then detecting them by Kleihauer testing in blood aspirated from the larger. Invasive procedures also yielded information on fetal blood gas measurements (acidaemia in four and hypoxaemia in six) and amniotic pressure (raised in two). We suggest that comparison of haemoglobin concentrations is inaccurate in fetofetal transfusion syndrome in utero, the diagnosis of which may necessitate detection of a shared circulation using a marker such as adult red cells.

Fetal disruptions: assessment of frequency, heterogeneity, and embryologic mechanisms in a population referred to a community-based stillbirth assessment program

The Wisconsin Stillbirth Service Project (WiSSP) is a community-based program for the investigation of the cause of fetal death. From its inception in 1983 through July 1988, 629 referrals were made to WiSSP. All referrals were assessed for the presence of disruptional characteristics, and 23 were found to have major or primary disruptive effects. Most of these were either early amnion disruption/limb-body wall disruption (treated as a single group, since analysis suggests a continuum of clinical characteristics) and twin-twin disruptions. Therefore, disruptions accounted for 3.6% of all referrals (including liveborn and miscarriage referrals) to WiSSP. When only stillborn fetuses are considered, approximately 2.4% appear to have died because of disruptions. This makes disruptions one of the most frequent, identifiable causes of late intrauterine death. We estimate that 0.6-1.4% of all stillborn fetuses die because of early amnion disruption/limb-body wall disruption which, when taken with previous estimates of the frequency of such problems in early miscarriages and liveborn infants, suggests that these disruptions result in a 95% prenatal mortality rate. We suggest a unified model of likely pathogenetic mechanisms which may help explain the continuum of multisystem involvement seen in those with early amnion disruption/limb body wall disruption. In addition, 3 patients with atypical disruptions are reviewed who exemplify the difficulty and importance of differentiating disruptional and malformational processes.

Monozygotic twin pregnancy: diagnostic and Doppler ultrasound studies

Of 178 consecutive twin pregnancies, 63 were both monozygotic and also studied prenatally by real-time B-scan (and usually Doppler) ultrasound. The 48 pregnancies with monochorionic placentas (in which vascular anastomoses are almost universal) were compared with the 15 monozygotic pregnancies having dichorionic placentas. The type of placenta found at delivery was predicted with substantial accuracy by ultrasound examination in mid-pregnancy. We were unable to identify any inter-group difference in fetal growth rate, discordance of fetal growth between twins or pattern of umbilical artery flow velocity waveform. In the absence of the rare florid twin transfusion syndrome, the vascular anastomoses that have been shown to be common in monochorionic placentas do not exert a strong influence on fetal growth or fetoplacental blood flow.

Ultrasonographic criteria for the prenatal diagnosis of placental chorionicity in twin gestations

Thirty-two patients with uncomplicated twin pregnancies had ultrasonographic examinations for genetic amniocentesis, confirmation of twinning, or assessment of fetal growth. The dividing membranes between the fetuses were visualized, and the thickness of the membranes was measured. With a thickness of 2 mm used as a cutoff point, the accuracy in predicting monochorionic or dichorionic twinning was 82% and 95%, respectively. Prenatal assessment of these dividing membranes may be helpful in the management of twin gestations.

Perinatal outcome in very preterm births with twin-twin transfusion syndrome

We retrospectively studied 48 pairs of twin gestations delivered between 24 and 28 weeks' gestation from 1975 to 1986 at Vanderbilt University Medical Center. The incidence of fetofetal transfusion syndrome was 20%, more than double the incidence previously reported in large series of twin deliveries that encompassed a wider gestational age range. The overall mortality was 55%, and mortality for the fetofetal transfusion group was 70%, whereas a subset of the fetofetal transfusion group, those without weight discordancy, had a mortality rate of 75%. Our findings suggest that traditional reliance on ultrasonographic criteria for diagnosis of fetofetal transfusion will not detect 40% of such cases. The poor outcome data suggest a need for innovative approaches to diagnosis and treatment.

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.

Fetal transfusion syndrome: antenatal factors predicting outcome

Fetal transfusion syndrome is a serious complication of monozygotic multiple pregnancy and is associated with a high perinatal mortality rate. Recent literature has outlined aggressive interventions that attempt to improve the outcome of these pregnancies. We identified 25 cases of fetal transfusion syndrome from 595 multiple pregnancies delivered between January 1983 and December 1987 at the Grace Hospital. Analysis of antenatal factors with respect to survival showed that gestational age at delivery, the presence of hydrops, and the use of decompression amniocentesis may help in predicting outcome. These factors may be useful in deciding on the appropriate therapeutic approach for a particular pregnancy.

The ultrasonographic prediction of chorionicity in twin gestation

In a prospective study of 69 consecutive twin gestations, chorionicity was assessed ultrasonographically, by the new technique of counting the number of layers visualized in the dividing membrane. For purposes of the study the antenatal categorization of chorionic type was based only on the number of layers observed. The pregnancy was classified as monochorionic when only two layers were identified and as dichorionic if three or four layers were seen. Confirmation of chorionic type was obtained after delivery by histopathologic examination of the placenta. The ultrasonographic technique used correctly determined chorionicity in 68 of 69 twin pregnancies. The predictive accuracy was 100% for 51 pregnancies designated by ultrasonography as dichorionic and 94.4% for 18 pregnancies considered to be monochorionic. These results suggest that counting the number of layers seen in fetal membranes by ultrasonography examination is an accurate way of determining chorionicity in twin gestation.

Prenatal diagnosis of Wiedemann-Beckwith syndrome

We report the prenatal diagnosis of Wiedemann-Beckwith syndrome in the 28th week of pregnancy in a primigravida. The cause of hospitalization was severe polyhydramnios with premature labour. Sonography revealed macrosomia, nephromegaly, cysts of adrenal glands and a striking macroglossia with opened mouth in all controls. The combination of all these symptoms suggested the prenatal diagnosis of Wiedemann-Beckwith syndrome, which could be confirmed post partum after a normal delivery in the 33rd week of pregnancy. The newborn (2700 g, 48 cm) exhibited typical features of this syndrome as moderate hypoglycemia and polycythemia in addition to the sonographic finding. Pathogenetic aspects and differential diagnosis of macrosomia are discussed.

Absence of detectable chromosomal and molecular abnormalities in monozygotic twins discordant for the Wiedemann-Beckwith syndrome

Monozygotic twins discordant for the Wiedemann-Beckwith syndrome (WBS) were studied by cytogenetic and molecular methods to determine if a genetic lesion could be detected in the affected child. Probes known to be localized on the short arm of chromosome 11 and a low copy-repetitive probe were used. No genetic lesions could be ascertained in normal or affected tissue obtained from the WBS twin.

Congenital focal glomerular lesions in only one monozygotic twin related to a probable twin transfusion syndrome

A case of congenital focal glomerular lesions involving crescent formation in only one monozygotic twin is reported. The possible effect of chronic hypotension in the pathogenesis of the lesion is discussed, considering the fact that the affected twin was probably the donor in a feto-fetal transfusion syndrome.

Timely diagnosis by cardiotocography of critical fetal reserve due to fetofetal transfusion syndrome

In a review of 90 twin pregnancies monitored by antenatal cardiotocography there were 8 cases of subsequently proven fetofetal transfusion syndrome. In 2 of these evidence of severe fetal stress had indicated immediate delivery; the 4 babies survived in circumstances that were perilous. In 1 case there was no evidence of critical fetal reserve but the recipient twin died, this probably representing an acute fetofetal transfusion during labour. In the 5 milder cases with no evidence of stress on cardiotocography, all babies survived and they required minimal or no treatment for problems relating to the fetofetal transfusion. In multiple pregnancy the cardiotocograph offers the additional bonus of detection of fetal compromise due to fetofetal transfusion.

Intra-uterine tachycardia associated with multicystic encephalomalacia (MCE)

Multiple cystic brain lesions in neonates have been described as a result of a variety of causes. All events described thus far in association with multicystic encephalomalacia (MCE) seem to point to hypoxic-ischaemic injury as the common factor for this particular form of central nervous system damage. We describe a neonate in whom repeated, prolonged episodes of intrauterine tachycardia had been documented. Congestive heart failure and fetal hydrops were present at birth and MCE at the age of 13 wk. The obvious relationship between this child's intrauterine tachycardia and his MCE points to the fact that any fetus with prolonged tachycardia should be considered at risk of severe brain damage.

Twin pregnancy with intrauterine death of one twin

The antepartum death of one twin is a rare obstetric complication. Two cases are presented, accompanied by a review of the current literature. The premature and neonatal death rates are high in the surviving twins. Toxemia, fetal distress, abnormal presentation, and dystocia are also increased. Maternal disseminated intravascular coagulation has been demonstrated without a concomitant fetal coagulation defect. A more unique finding is fetal disseminated intravascular coagulation with a monochorionic placenta. The common circulation between the live and dead twins may result in fetal cerebral, renal, and cutaneous lesions, usually without demonstrable maternal disease. High-risk obstetric management is reviewed and a careful pediatric follow-up is recommended with monozygotic twins.