Managing twins discordant for fetal anomaly

An excess of structural anomalies is observed in twins compared to singletons. Approximately 1–2% of twin pregnancies may face the dilemma of expectant management versus selective termination following diagnosis of an anomaly affecting only one fetus. If the option of selective fetocide is considered, the main variable determining the technique to achieve this aim is chorionicity. In a dichorionic pregnancy, passage of substances from one twin into the circulation of the co-twin is unlikely due to the lack of placental anastomoses, hence KCl can be injected safely into the circulation of the affected twin to produce fetal asystole. In monochorionic twin pregnancies, selective termination needs to be performed by ensuring complete and permanent occlusion of both the arterial and venous flows in the umbilical cord of the affected twin, in order to avoid acute haemorrhage from the co-twin into the dying fetus, which may lead to death or organ damage. Bipolar cord coagulation under ultrasound guidance is associated with approximately 70–80% survival rates. Copyright © 2005 John Wiley & Sons, Ltd.     

Prenatal diagnosis of female monozygotic twins discordant for Turner syndrome: implications for prenatal genetic counselling

We describe a set of monozygotic (MZ) female twins, one of whom presented with a typical Turner syndrome (TS) phenotype and the other a normal female phenotype. Prenatal fetal ultrasonographic examination showed a monochorial diamniotic pregnancy with a hygroma colli and growth delay in Twin A and no anomalies in Twin B. Karyotypic analysis performed on fetal blood samples demonstrated a 46,XX/45,X (23/2) mosaicism in Twin A and a normal 46,XX chromosome constitution in Twin B. At birth, Twin A presented with a typical TS and Twin B had a normal female phenotype. Postnatal cytogenetic investigation of blood lymphocytes showed the same 46,XX/45,X mosaicism in both twins: 46,XX/45,X (40/7) in Twin A and 46,XX/45,X (40/5) in Twin B. Further investigations at the age of 10 months showed in Twin A a 46,XX/45,X (98/2) mosaicism in lymphocytes and 100% of 45,X (50 analysed cells) in fibroblasts, and in Twin B a normal 46,XX (100 analysed cells) chromosome constitution in lymphocytes but a mild 46,XX/45,X (78/2) mosaicism in fibroblasts. Monozygosity was confirmed by molecular analysis. To our knowledge, this is the first report of prenatal diagnosis of MZ female twins discordant for TS. Review of reported sets of MZ female twins (eight cases) or triplets (one case) discordant for TS shows, as in the present case, that the phenotype correlates better with the chromosomal distribution of mosaicism in fibroblasts than in lymphocytes. In the blood of MZ twins chimerism may modify the initial allocation of the mosaicism. These results suggest that, in cases of prenatal diagnosis of MZ female twins discordant for TS, the phenotype of each twin would be better predicted from karyotype analysis of cells from amniotic fluid than from fetal blood. Copyright © 2002 John Wiley & Sons, Ltd.     

Combining nuchal translucency and serum markers in prenatal screening for Down syndrome in twin pregnancies

A method is described to combine the ultrasound marker nuchal translucency (NT) with serum markers so that they can be used together in prenatal screening for Down syndrome in twin pregnancies. For monochorionic twin pregnancies (taken as monozygous), the two fetus-specific NT measurements are averaged before risk is calculated and before the contribution of the serum markers is incorporated. For dichorionic twin pregnancies (taken as dizygous), the risk for each fetus based on the individual NT measurements is calculated, the two fetus-specific risks are added together, and then the contribution of the serum markers is incorporated. In this way, all the screening markers can be used in combination to produce a pregnancy-specific ‘pseudo-risk’, rather than a fetus-specific pseudo-risk. We refer to pseudo-risk because in the absence of sufficient data on the screening markers in affected twin pregnancies, a true risk estimate cannot be calculated. Tentative estimates are given of screening performance in twins using NT, the combined test (NT with first-trimester serum markers), and the integrated test (NT with first- and second-trimester serum markers), all interpreted with maternal age. Copyright © 2003 John Wiley & Sons, Ltd.     

Monochorionic and dichorionic twin pregnancies discordant for fetal anencephaly: a systematic review of prenatal management options

The aim of this study was to evaluate the effect of selective feticide (SF) compared to expectant management (EM) on perinatal outcome in dichorionic and monochorionic twins discordant for anencephaly. For this purpose, we conducted a systematic review of literature and added ten unpublished cases. As a result, we found that in dichorionic twins, mean gestational age (GA) at birth in the SF group was 38.0 weeks versus 34.9 weeks (P = 0.0002). Mean birth weight was 2922 g in the SF group versus 2474 g (P = 0.03). In monochorionic twins, mean GA at birth was 35.2 weeks versus 32.7 weeks (P = 0.1). Mean birth weight was 2711 g versus 1667 g (P = 0.0001). We conclude that while SF does not reduce perinatal mortality, it does result in significantly longer gestations and higher birth weight, and appears to be the management of choice in dichorionic twins discordant for anencephaly. In monochorionic twins, SF also increases birth weight, but in view of the complexity of this group, no clear recommendations can be made. Copyright © 2008 John Wiley & Sons, Ltd.     

Conjoined twins

Conjoined twins have been a source of fascination for both the general public and the medical profession since time immemorial. Their birth was initially viewed as an ominous sign of impending disaster. This was followed by a prolonged period through the Middle Ages and into the nineteenth century when they were regarded as freaks or monstrosities and were exhibited with substantial financial reward at circuses and sideshows. Recently, conjoined twins have attracted intense media interest, which has coincided with increasing success in their separation. This article gives an overview of the role of prenatal ultrasound in assessing the prognosis and discusses the post-natal surgical management and outcome. Copyright © 2005 John Wiley & Sons, Ltd.     

Fetal exsanguination following intrauterine angiographic assessment and selective termination of a hydrocephalic,monozygotic co-twin

Selective termination by intracardiac potassium chloride injection was performed in twins discordant for hydrocephaly at 20 weeks' gestation. Because of the potential for vascular anastomoses to exist between the twins, fetal angiography was performed prior to the selective termination procedure. Determination of vascular connections between the fetuses was hindered by fetal bradycardia following intracardiac administration of contrast material. Selective termination was performed without difficulty using intracardiac potassium chloride (KCl) to produce asystole in the twin with hydrocephaly. The unaffected fetus appeared active and had a normal heart rate during and immediately after the procedure. However, both twins were found to have died the following day. Pathologic examination documented several vascular anastomoses between the monochorionic, diamniotic fetuses. A likely cause of death was exsanguination of the normal twin into the abnormal one. This case illustrates the difficulties encountered in selective termination of monozygotic twins and, to our knowledge, represents the first reported use of intrauterine fetal angiography.     

Prenatal diagnosis of a rare heteropagus

The prenatal diagnosis by ultrasound of an unusual case of supernumerary head is reported. The problems of differential diagnosis, the pathological findings after voluntary interruption of the pregnancy, and the problems of obstetric management are presented.     

Update on selective reduction

Over the past 25 years fetal reduction has been utilized to reduce the risks of higher-order multiple pregnancies that have resulted from overly successful infertility therapies. The demographics of multiple pregnancy patients have evolved over the past decade, with increasing proportions coming from IVF as opposed to ovulation induction, being older and a higher proportion with donor eggs. Genetic diagnosis prior to reduction is becoming more common and is very safe in experienced hands. For all starting numbers, including twins, reduction to a lower number of fetuses reduces fetal losses, prematurity, and infant mortality and morbidity. Copyright © 2005 John Wiley & Sons, Ltd.