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Outcome of pregnancies affected by Twin to Twin Transfusion Syndrome identified within the Southampton Fetal Medicine Service 1997-2005

Presented at the Neonatal Society 2007 Summer Meeting (programme).

O’Donnell AI1, Connor J2

1 Department of Neonatal Medicine and Surgery, Princess Anne Hospital, Coxford Rd, Southampton SO16 5YA, UK
2 Department of Obstetrics, Princess Anne Hospital, Coxford Rd, Southampton SO16 5YA, UK

Background: Twin to twin transfusion syndrome (TTTS) affects around 15% of monochorionic diamniotic twin pregnancies (MCDA). Left untreated, mortality/serious morbidity approaches 100%. Antenatal intervention with serial amnioreduction or laser ablation of communicating vessels has been shown to improve outcome with survival rates of 50-69%. However, significant rates of morbidity are seen in survivors with neurodisability rates of 25% following amnioreduction and 5-11% following laser ablation.

Purpose of study: To ascertain regional outcomes for pregnancies affected by (TTTS).

Methods: Two retrospective reviews of pregnancies affected by TTTS referred to the Wessex Fetal Medicine Service between 1997-2001 and 2002-5 and were undertaken in accordance with UK ethical guidelines. During time period 1 serial amnioreduction was the only treatment offered but in period 2 early TTTS (stage1 and 2) was treated with amnioreduction and more severe or non-responsive disease being referred for laser ablation. Patients were identified via the fetal medicine database and data collated by a combination of note and database review.

Results: Overall 56 pregnancies were affected by TTTS. In period 2 this represented 19.8% of all MCDA pregnancies. 62% of cases were diagnosed before 20 weeks. In period 1 one patient received laser treatment whilst in the second period 33% received laser treatment +/- amnioreduction. Average age at delivery was 29.8 weeks but where both twins survived average gestation was 32.9 weeks and where neither twin survived 23.5 weeks. 69% were liveborn (64%/77%) with overall survival rates of 53% and 58%. Of babies dying in the neonatal period the average gestation at delivery was 26 weeks and average birthweight 586g.

As expected significant morbidity was seen in liveborn infants. Over 50% showed evidence of renal impairment half of which was severe. During period 1 8.7% of infants required dialysis and one infant is likely to develop end stage renal failure in childhood. No babies required dialysis in the second cohort. There were high rates of early echocardiographic abnormalities and 15% of survivors showed significant ventricular hypertrophy or tricuspid regurgitation and 20% significant hypertension. Ischaemic complications were not uncommon with 7.5% developing necrotising enterocolitis and 9.3% affected by limb ischaemia including antenatal ischaemic below knee amputation.

Ultrasound changes suggestive of cerebral ischaemia were seen in 14.8% with the development of cystic periventricular leukomalacia in 8.7%. Only one infant has been identified as having cerebral palsy on follow up (2%) but ascertainment is not complete.

Conclusion: Survival rates for infants are comparable with published data. TTTS is associated with significant mortality and morbidity. Neurological morbidity is well recognised but other organ damage can also be associated with poor outcome.

1. Cincotta R B et al, Arch Dis Child Fetal Neonatal Ed 2000; 83:F171-F176
2. Lenclen R et al, Am J Obstet Gynecol. 2007 May; 196(5).450.e1-7

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