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.     

The sonographic diagnosis of chorionicity

The differentiation between mono- and dichorionic placentation in twin pregnancies is of clinical importance because of the significant difference in perinatal morbidity and mortality between the two, and the increased surveillance indicated in monochorionic gestations. Application of ultrasonography has enabled very precise prenatal determination of chorionicity. While this is best performed in the first trimester when accuracy approaches 100%, even in the third trimester, using a composite cascade of available sonographic features, accuracy has been reported to approach 97%. While two clearly separate placentae or discordant fetal gender conform to dichorionicity, in most twin pregnancies other features need to be assessed to determine chorionicity. The presence of the ‘lambda’ or the ‘T’ sign in the presence of a single placenta, best determined in the first trimester, is the most reliable indicator of chorionicity, with measurements of the inter-twin membrane thickness and counting of the membrane layers being less reliable. In this article, we review the sonographic features that help in the accurate depiction of chorionicity. Copyright © 2005 John Wiley & Sons, Ltd.     

Discordant growth in twins

Discordant growth in twins contributes significantly to rates of perinatal morbidity and mortality. These rates vary according to chorionicity, timing of onset and severity. We have reviewed English language literature in Medline since 1980. It is clear that diagnosis of discordant growth has improved due to the use of serial ultrasound examination. Following the detection of differences in fetal size, diagnosis is facilitated by umbilical artery and fetal Doppler studies. Management options vary according to chorionicity, timing of onset and umbilical-fetal Doppler studies. The mode of delivery in discordant twins remains controversial. We conclude that ultrasound surveillance of twin gestations, combining serial biometry and selective Doppler studies, is effective in the recognition of siginificant intrauterine growth restriction in co-twins. Differences in etiology and management underscore the imortance of establishing chorionicity routinely as soon as twin gestation is diagnosed. Copyright © 2005 John Wiley & Sons, Ltd.     

Psychological aspects of prenatal diagnosis and its implications in multiple pregnancies

Couples expecting twins are often unrealistically optimistic and are therefore unprepared for the complications as well as the practical and emotional impact the birth of twins can have on the family. All such couples will need information and support throughout the pregnancy and beyond. In this review, the various aspects that should be addressed are discussed, in particular, health care workers and counsellors need to be aware of the stress experienced by parents who have been through prolonged treatment for infertility or who face the special problems associated with the loss of one twin (implies the loss could be other than death). Copyright © 2005 John Wiley & Sons, Ltd.