T. Vanderheyden

Twin-twin transfusion syndrome: the influence of intrauterine laser photocoagulation on arterial distensibility in childhood.

Background—In twin-twin transfusion syndrome (TTTS), the donor and recipient fetus are exposed to differing volume loads and show discordant intertwin vascular compliance in childhood despite identical genotype. We hypothesized that discordance is prevented by intrauterine endoscopic laser ablation of placental anastomoses, which abolishes intertwin transfusion. We tested this by examining pulse wave velocity (PWV) in brachial arteries of twin survivors of TTTS treated with and without laser therapy. Methods and Results—One hundred children (50 twin pairs, 27 with TTTS) were studied. Group 1 comprised 14 monochorionic (MC) twin pairs with TTTS treated symptomatically; group 2 comprised 13 MC twin pairs with TTTS treated by laser. The control groups comprised 12 MC twin pairs without TTTS (group 3) and 11 dichorionic twin pairs (group 4). Fetal cardiovascular data, predictive factors for, and duration of TTTS and cord blood were collected prospectively. We measured blood pressure and PWV photoplethysmographically at a median corrected postnatal age of 11 months (range, 1 week to 66 months). Both TTTS groups showed marked intertwin PWV discordance, unlike MCDA control subjects. The PWV discordance seen in laser treated twin pairs resembled that of dichorionic control subjects (heavier individual with higher PWV), whereas group 1 showed the opposite (negative) intertwin discordance (ANOVA F (1,45)=4.5, P =0.04). No significant differences in blood pressure or intrauterine growth were observed between TTTS groups. Conclusions—Vascular programming is evident in monozygotic twins with intertwin transfusion and is altered but not abolished by intrauterine therapy to resemble that seen in dichorionic twins.

Fetal renal impairment

Renal function in utero deals chiefly with urine production rather than the excretion of metabolites, which are cleared by the placenta. Fetal renal impairment (FRI) in bilateral renal disease thus presents as oligohydramnios or anhydramnios; this can lead to lung hypoplasia and early neonatal death. As in the adult, FRI can be divided into prerenal, renal and postrenal causes. Causes of prerenal FRI include intrauterine growth restriction, unbalanced intertwin transfusion in monochorionic twins and maternal drug ingestion. Bilateral renal agenesis, multicystic dysplasia and both the autosomal dominant and recessive forms of polycystic kidney disease are examples of renal causes, whereas postrenal etiologies are usually caused by lower urinary tract obstruction (LUTO). When both kidneys are affected and there is severe mid-trimester oligohydramnios, the prognosis is poor. Although animal studies have shown that prolonged LUTO leads to lung hypoplasia and renal damage, and that decompression of the fetal kidney in early pregnancy restores fetal pulmonary and renal function, the value of fetal therapy such as vesico-amniotic shunting remains controversial, with a high procedure-related complication rate and a high incidence of end-stage renal failure in childhood. Fetal cystoscopic treatment of posterior urethral valves in utero may obviate some of these difficulties but remains an investigational procedure.

Transmitted arterio-arterial anastomosis waveforms causing cyclically intermittent absent/reversed end-diastolic umbilical artery flow in monochorionic twins.

OBJECTIVES To characterize the phenomenon of retrograde transmission of arterio-arterial anastomosis (AAA) interference patterns on umbilical artery (UA) waveform by (a) documenting the periodicity, (b) correlation with in vivo and in vitro demonstration of AAAs and (c) reproducing these patterns by computer modelling. METHODS Monochorionic twins (MC) twins underwent placental and umbilical Doppler studies. AAAs were sought by pulse wave Doppler of their bi-directional interference pattern and confirmed by postnatal injection studies. The periodicity of transmitted patterns in the UA was determined. Determinants of the transmitted patterns were ascertained by computer modelling of physiological and fetal variables. RESULTS Among 83 prospectively studied MC twin pregnancies; a transmitted pattern was observed in 6 (7 per cent) patients for 15-114 days. This was found in 20 per cent (6/30) of smaller MC twins discordant for growth restriction but in no appropriately grown twins. It was only observed in association with AAAs validated both in vivo and in ex vivo. Computer modelling demonstrated that this pattern could be reproduced by summating end diastolic flow with a high pulsatility index in the UA in the presence of a large AAA. Consistent with this, MC twins with a transmitted pattern had larger AAAs (median diameter 4.3 mm interquartile range 4.1-5.2) compared to MC twins discordant for intrauterine growth restriction (2.1 mm interquartile range 1.5 to 2.8) (P<0.05) without a transmitted pattern. Perinatal mortality was similar in the fetuses with and without transmitted patterns (0/12 vs. 2/48 P=0.7).

Doppler for artery-artery anastomosis and stage-independent survival in twin-twin transfusion.

OBJECTIVE: Treatment selection in twin–twin transfusion syndrome is increasingly determined by disease severity. We investigated whether detection of arterio-arterial anastomoses predicts perinatal survival. METHODS: An artery–artery anastomosis was sought by Doppler and disease stage was determined in 105 cases of twin–twin transfusion syndrome at presentation, first treatment, and worst stage. Outcome measures were perinatal, double, and any (1 or more babies) survival rates. RESULTS: After exclusion of 10 noninformative pregnancies, perinatal, double, and any survival rates were 61%, 44%, and 77%, respectively. When an anastomosis was detected at each of the 3 time points, perinatal and double survival rates were higher than when one was not (at first treatment, perinatal survival 83% versus 53%, respectively, P = .003; double survival 78% versus 33%, P < .001). Perinatal and double survival (P ≤ .01) were poorer with more advanced stage, but any survival rates were not influenced by stage or anastomosis detection. Multiple logistic regression demonstrated that anastomosis detection at treatment increased the chance of perinatal (odds ratio [OR] 5.1, 95% confidence interval [CI] 1.6, 15.9) and double survival (OR 19.3, 95% CI 2.7, 138), independently of stage. For stages I–III at treatment, anastomosis detection predicted better perinatal (100% versus 63%, 100% versus 59%, and 83% versus 44%, respectively) and double survival rates (100% versus 52%, 100% versus 46%, and 78% versus 26%). Stage III, with anastomoses detected, had better perinatal (83% versus 63%) and double survival (78% versus 52%) than did stage I without detection. CONCLUSION: Antenatal detection of artery-to-artery anastomosis predicts higher perinatal and double survival in twin–twin transfusion syndrome, independently of disease stage. LEVEL OF EVIDENCE: II-3

Increased latency of absent end‐diastolic flow in the umbilical artery of monochorionic twin fetuses

To determine if absent end‐diastolic flow (AEDF) in the umbilical artery (UA) has a longer latency in monochorionic (MC) twin fetuses compared to singleton or dichorionic twin (DC) fetuses.

OC227b: Doppler detection of arterio‐arterial anastomosis predicts survival outcome independent of Quintero stage in TTTS

Objectives: 1) To assess the accuracy of fetal echocardiography in multiple pregnancy, and 2) To evaluate the type of congenital heart disease (CHD) and of extracardiac anomalies detected in 36 cases of multiple pregnancy. Method: We analysed a population of 248 pregnancies (546 fetuses, 39 with CHD). Diagnostic accuracy was calculated for fetal echocardiography. In fetuses with CHD, the following variables were analysed: chorionicity, gestational age at diagnosis, type of CHD, associated chromosomal and extracardiac abnormalities, fetoneonatal outcome. Results: In this series, sensitivity was 88.8%, specificity 99.8%, PPV 97.1% and NPV 99.1%. There were 4 FP and 1 FN cases. The association with aneuploidy was 9.3% (3/32). The spectrum of CHD was similar to that seen in singleton during the same period of time. Of note, that 8/32 (25.0%) fetuses with CHD were recipients from monochorionic pregnancies complicated by TTTS. As for the outcome, 21 (65.6%) neonates survived and 11 (34.4%) died prior to (9) or after surgery (2). Conclusions: Fetal echocardiography is clearly feasible also in multiple pregnancy without particular difficulties, at least for twins. In triplets and quadruplets, fetal crowding makes things a great deal more difficult. The association with aneuploidy is lower than expected, possibly due to the low incidence of extracardiac anomalies in this series and to the relatively small number of cases. As to the outcome, low birthweight coupled with CHD seem to be an important bad prognostic indicator, be it for growth restriction or simply prematurity.

OP05.14: Interstitial intrafetal laser for selective and non‐selective reduction in complicated monochorionic multiple pregnancies

of both twins occurred in the first 72 hours. Among the remaining 21 cases, two pregnancies are ongoing and beyond 28 weeks. The mean gestational age at delivery of the remaining 19 cases was 31.2 weeks (range, 25–36) and the mean birthweight of the liveborns was 1584 g (range, 460–3800). Overall, both fetuses were born alive in 46% (11/24) of cases, only one fetus was born alive in 33% (8/24), and neither was born alive in the remaining 20% (5/24). 24 of the 30 (80%) nfants born alive survived the perinatal period, yielding an overall perinatal survival rate of 50%. All neonatal deaths were associated with extreme prematurity. Conclusions: Selective laser coagulation appears to be a good treatment option in cases of severe TTTS, but requires technical skills and adequate equipment. Training in identifying the vascular anastomoses is essential before attempting the procedure as this is a critical step in achieving success. Prematurity and its consequences remain major drawbacks. Long-term follow-up, currently underway in our series, is necessary to assess the rate of cardiac and neurological sequelae in the surviving infants.

P349: Interstitial laser for vascular occlusion of fetal vasculature

the largest vertical amniotic fluid pocket of 14 cm. No obvious foetal anomalies were observed. Subsequent ultrasound evaluation at 22 weeks’ gestation revealed persistent polyhydramnios, a 51% discordance in the estimated foetal weights, and a significantly larger foetal bladder in the larger twin. TTTS was highly suspected, despite the absence of the polyhydramnios-oligohydramnios sequence. Foetal surgery with placental laser ablation of vascular anastomoses was planned, but at 23 weeks’ gestation, demise of both twins was noted. Pathological examination confirmed the diagnosis of TTTS. This case illustrates that in MM twin gestations, the diagnosis of TTTS can be made even in the absence of the polyhydramniosoligohydramnios sequence, as this finding cannot be appreciated without a dividing membrane. Twin-twin transfusion syndrome represents an additional hazard in MM twin pregnancies.

P343: Longer latency of AEDF in monochorionic twins

20–24 weeks anatomic scans), biochemical screening (first and/or second trimester), or amniocentesis. Results: Ten women were eligible for study. The mean gestational age at diagnosis was 37 weeks (range 35–40 weeks). The distribution of findings by systems was: central nervous system (CNS) (5), suspected systemic viral infection (1), gastrointestinal (GI) (2), renal (1), and cardiovascular (1). One woman with acute onset of massive hydrocephalus and increased ICP at 36 weeks gestation had an urgent cesarean section, and the neonate had a ventriculoperitoneal shunt. One woman with diffuse fetal cerebral cortical damage and an occipital cyst diagnosed at 40 weeks gestation terminated the pregnancy at another hospital. One neonate with a spinal cystic mass was operated on successfully. All infants are developing normally to date (range of follow-up 6 weeks to 18 months). Two pregnancies are still ongoing at 37 and 39 weeks gestation. Conclusions: This diverse group of patients manifests the importance of late third trimester diagnosis of fetal anomalies for the management and treatment of affected pregnancies. It is necessary to consider the benefit of performing another fetal anatomic scan by a specialist in the third trimester. Furthermore, the ethical implications of late third trimester pregnancy termination must be dealt with.

Posterior fossa pathology: high-resolution US vs. fetal MRI

Fetal MRI is claimed to be superior to US for diagnosing posterior fossa pathology. In contrast, our experience is that US allows better visualisation of the cerebellum, thus facilitating diagnosis. Thirteen fetuses with posterior fossa pathology were offered a fetal MRI (0.5 Tesla Philips Apollo MR system) following detailed high-resolution ultrasound (Acuson Sequoia TM 512). Three patients were diagnosed on US with classic Dandy-Walker (CDW), four with Dandy-Walker variant (DWV), three with enlarged cysterna magna (CM) and in three patients other cerebellar pathology was suspected. In 11 of 13 (85%) fetuses, the MRI did not provide additional information. In one fetus with CDW, the MRI confirmed the lesion and in addition showed agenesis of the corpus callosum, but did not change management. In one of the first MRIs on a fetus with DWV, the lesion in the vermis of the cerebellum could not be visualised and this changed the management. Our experience is that small vermal defects or subtle lesions in the posterior fossa are very difficult to visualise on MRI before 24 weeks, because of slice thickness and fetal movements. In these cases US seems superior.