Twin-to-twin transfusion syndrome occurs when unborn identical twins have different sacs in the womb but share the same placenta. This may result in blood flow from one twin to the other through connections between blood vessels in the shared placenta. The volume of fluid around the twins can also become uneven. In amnioreduction using septostomy, a needle is used to make a hole in the membrane separating the twins to even out the volume of the fluid surrounding the babies. Sometimes excess amniotic fluid may need to be removed with another needle (this procedure is called amniodrainage).

The National Institute for Health and Clinical Excellence is examining amnioreduction using septostomy with or without amniodrainage for the treatment of twin-to-twin transfusion syndrome and will publish guidance on its safety and efficacy to the NHS in England, Wales, Scotland and Northern Ireland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisers, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about amnioreduction using septostomy with or without amniodrainage for the treatment of twin-to-twin transfusion syndrome.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

• comments on the preliminary recommendations
  
• the identification of factual inaccuracies
  
• additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows.

• The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
  
• The Advisory Committee will then prepare draft guidance which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales, Scotland and Northern Ireland.

For further details, see the Interventional Procedures Programme manual, which is available from the Institute's website (www.nice.org.uk/ipprogrammemanual).

Closing date for comments: 26 September 2006
Target date for publication of guidance: January 2007

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

Current evidence on the safety and efficacy of amnioreduction using septostomy, with or without amniodrainage, for the treatment of twin-to-twin transfusion syndrome (TTTS) does not appear adequate for this procedure to be used without special arrangements for consent and for audit or research.

Clinicians wishing to undertake amnioreduction using septostomy, with or without amniodrainage, for the treatment of TTTS should take the following actions:

• Inform the clinical governance leads in their Trusts.
• Ensure that the parents understand the uncertainty about the safety and efficacy of the procedure, and the range of treatment options available. The parents should also understand that in spite of amnioreduction, there is still a risk of serious abnormalities in the development of the nervous system among survivors of TTTS. Clinicians should provide parents with clear written information. Use of the Institute's information for patients ('Understanding NICE guidance') is recommended (available from www.nice.org.uk/IPGXXXpublicinfo). [[details to be completed at publication]]
• Audit and review clinical outcomes of all patients having amnioreduction using septostomy with or without amniodrainage for the treatment of TTTS (see section 3.1).

Clinicians should consider case selection carefully because there is uncertainty about the stages of TTTS for which this procedure is appropriate.

This procedure should only be performed in centres specialising in fetal medicine and in the context of an appropriate multidisciplinary team.

Clinicians are encouraged to collaborate on longer term data collection across the centres performing amnioreduction for the treatment of TTTS. The Institute may review the procedure upon publication of further evidence.

Approximately 70% of monozygotic twins are monochorionic/diamniotic (one placenta with two amniotic sacs). TTTS affects approximately 15% of these pregnancies, and perinatal mortality is up to 80% if the syndrome is left untreated. TTTS results from shunting of blood between the circulations of the unborn twins through anastomoses of the vessels of the shared placenta. Blood is transfused from the donor twin, whose growth becomes restricted and who develops oligohydramnios or anhydramnios (low or absent amniotic fluid), to the recipient, who develops circulatory overload, cardiac compromise and polyhydramnios (too much amniotic fluid). The combination of polyhydramnios in the recipient and oligo/anhydramnios in the donor squashes the donor twin against the wall of the uterus. The syndrome is generally associated with high morbidity and mortality for both twins. Morbidity among survivors includes cardiac, renal and serious neurological impairment, such as cerebral palsy. About 15% of survivors have long-term neurological sequelae.

The options for managing TTTS include expectant medical management, amniodrainage, septostomy, laser ablation, and selective fetal termination using techniques such as umbilical cord occlusion. In some cases the treatment aim is to enable one twin to survive, as the chances for both surviving are extremely poor. Some parents may choose to terminate the pregnancy because of the high risk of perinatal morbidity and mortality in both twins and the risks of serious long-term morbidity in survivors.

In one randomised controlled trial that included 36 twin pregnancies treated with amniodrainage and 35 treated with septostomy with or without amniodrainage, perinatal survival of at least one twin (measured until hospital discharge) was similar in both groups (78% [28/36] in the amniodrainage group versus 80% [28/35] in the septostomy group; relative risk [RR] 0.94, 95% confidence interval [CI] 0.55 to 1.61, p = 0.82). Survival of both twins was 50% (18/36) in the amniodrainage group compared with 60% (21/35) in the septostomy group (RR 0.82, 95% CI 0.52 to 1.30, p = 0.40). In a cohort study, perinatal survival of both twins was 43% (3/7) in the amniodrainage group compared with 57% (4/7) in those who underwent septostomy with or without amniodrainage. Survival of at least one twin was 86% (6/7) in both groups. Overall survival for amniodrainage alone was 9/14 (64%), versus 10/14 (71%) in the septostomy group; this difference was not statistically significant.

In four case series, overall perinatal survival (the total number of babies born alive divided by the total number of affected fetuses) ranged from 46% (12/26) to 83% (20/24). The differences in survival reported among the studies may be attributed to varying severity of TTTS, the studies that included more severe cases reporting poorer results.

Mean gestational age at delivery ranged from 27 to 31 weeks. Both comparative studies reported that pregnancy was prolonged following septostomy compared with amniodrainage alone. In the cohort study this difference was significantly different between the two groups, although this could be attributed to differences in severity of TTTS. Long-term neurological outcomes were not reported in the studies. For more details, refer to the sources of evidence (see appendix).

The Specialist Advisers commented that the best treatment for early-stage TTTS is still unclear. They noted that results from the two comparative studies indicate no significant advantage of septostomy and amniodrainage over amniodrainage alone.

The safety evidence is based on one randomised controlled trial and two case series. In general, safety data were not well reported in the studies.

In the randomised controlled trial, there were two cases of disruption of the intertwin membrane resulting in a monoamniotic twin gestation (one in each study arm). This complication has also been reported in two case reports. In a case series of 13 pregnancies, one woman went into spontaneous labour following septostomy and amniodrainage. This was thought to be related to placental damage. For more details, refer to the sources of evidence (see appendix).

One Specialist Adviser considered septostomy and amniodrainage to be a safe procedure, and noted that septostomy is often performed unintentionally during standard amniodrainage. All three Specialist Advisers highlighted that cord entanglement is a theoretical complication of septostomy.

This guidance requires that clinicians undertaking the procedure make special arrangements for audit. The Institute has identified relevant audit criteria and is developing an audit tool (which is for use at local discretion), which will be available when the guidance is published.

The Institute is developing interventional procedures guidance on intrauterine laser ablation of placental vessels for the treatment of twin-to-twin transfusion syndrome (www.nice.org.uk/ip_336).

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

• 'Interventional procedure overview of amnioreduction using septostomy with or without amniodrainage for the treatment of twin to twin transfusion syndrome', June 2006.