Monochorionic diamniotic placentation is, in 10-15% of cases, associated with the serious condition known as Twin-Twin Transfusion Syndrome. In this condition the twins share a single placenta and an imbalance in blood flow from one twin to the other can occur, resulting in marked differences in amniotic fluid volumes and fetal growth. Despite the efforts of current obstetric and neonatal management practices, Twin-Twin Transfusion Syndrome remains a condition associated with high perinatal mortality and morbidity rates. Indeed, it is considered one of the major challenges in contemporary perinatal medicine.

In 1995 the Australian and New Zealand Twin-Twin Transfusion Syndrome Register was established under the auspices of the Women and Infants Research Foundation. Data on the incidence, management and outcome of 112 cases were collected between 1995 and 1998, providing for the first time, a large body of data on this condition from a national perspective. The first international multicentre, randomised, controlled clinical trial of therapies for Twin-Twin Transfusion Syndrome was commenced in 1998 and completed in 2002. Known as “Twin-Twin Transfusion Syndrome (TTTS): A Multicenter Randomized Trial for the Evaluation of Septostomy vs Serial Amnioreduction for Therapy” this research study involved centres in the North America, Europe and Australia. King Edward Memorial Hospital actively participated in this trial and recruited the second largest number of participants to the trial. The results of this trial, which demonstrated a small benefit from septostomy, the deliberate creation of a connection between the twin sacs, is soon to be published.

In 1999, the Women and Infants Research Foundation provided funding for a study to assess the medium and long-term outcome of infants following Twin-Twin Transfusion Syndrome and the impact of this disorder on their families. Short-term outcome data have been collected from all families who had pregnancies complicated by this syndrome. We have assessed the children’s physical, emotional and behavioural development. This long-term assessment of neurologic status of surviving twins from pregnancies complicated by TTTS has demonstrated a reduction in IQ, especially in the very preterm children but no excess of behavioural disturbances or cerebral palsy in survivors compared with a contemporaneous Western Australian gestation-matched cohort.

There has been a large volume of research internationally into therapies for Twin-Twin Transfusion Syndrome. Collaborative research with Dr Ruben Quintero at the Fetal Therapy and Surgical Center in Tampa, Florida, USA has demonstrated amnioreduction therapy (withdrawal of large volumes of amniotic fluid from the sac of the recipient fetus) is an effective therapy in early Stage Twin-Twin Transfusion Syndrome, but as the disease progresses this therapy is less effective. For later stage disease laser photocoagulation of the communicating placental vessels appear to be a more successful treatment option.

Based on the results of this research, in 2002 we established a placental laser treatment centre for severe Twin-Twin Transfusion Syndrome through the Maternal-Fetal Medicine Service of King Edward Memorial Hospital. Laser photocoagulation therapy for severe Twin-Twin Transfusion Syndrome is now available in Western Australia, one of only a few centres in Australasia able to provide this treatment. Placental laser therapy involves the fetoscopic ablation of the shared blood vessels in the placenta of the two fetuses. In 2004 the Eurofetus group published a randomised controlled trial of this therapy compared with serial amnioreduction therapy, demonstrating an improved outcome with this treatment. Unfortunately, the results in both groups were still less than optimal and much work remains to be done to optimise therapies for this condition.

Data on the progression of disease severity in Twin-Twin Transfusion Syndrome have recently been published by our research team. These data have been of assistance in developing the concept of tailoring the therapeutic intervention required in Twin-Twin Transfusion Syndrome for the severity of the disease, to minimize complications and optimise maternal and perinatal outcomes. It is our belief that the management of Twin-Twin Transfusion Syndrome is not a “one-size-fits-all” concept and our current practice is to select the therapeutic option on the individual case characteristics.

A second severe complication of the monozygotic twinning process is monoamniotic twins, in which both fetuses share the same amniotic sac. Interestingly, this complication is increasing in frequency throughout the world, probably secondary to an as yet undetermined environmental factor. There is a 20-30% fetal abnormality rate in monoamniotic twins, and interestingly the anomalies are not typically concordant with usually only one of the pair being affected. The perinatal mortality rate for this condition is about 10-15% in structurally normal fetuses, with complications of cord entanglement accounting for 50% of these losses. Current concepts of management centre on preventing lethal umbilical cord compression and delivery at 32-34 weeks gestation. Clearly, if we could identify the pregnancies at risk of complications with greater accuracy, the need for preterm delivery would be reduced.

Multiple pregnancies pose a significant challenge to contemporary obstetric and neonatal practice. Ongoing research is central to reducing the complications of twin pregnancies, particularly reducing the preterm birth rate, optimising the management of Twin-Twin Transfusion Syndrome and reducing the perinatal loss rates of monoamniotic twins. As the incidence of this most complex form of twin pregnancy progressively rises, epidemiologic studies to investigate the potential reasons for the increase in monochorionic twinning are required.