Uncommon complications of monochorionic twin pregnancies: Twin anaemia-polycythaemia sequence

Twin anaemia-polycythaemia sequence (TAPS) occurs when significant haemoglobin discordance exists between monochorionic fetuses. Most reported cases occur iatrogenically after twin-to-twin transfusion syndrome (TTTS) laser therapy; spontaneous TAPS is also reported. The purpose of this study was to investigate pregnancy management and immediate neonatal outcomes for monochorionic multiple pregnancies complicated by TAPS referred to the NSW Fetal Therapy Centre (FTC).

Retrospective cohort study of multiple pregnancies referred to NSW FTC between April 2006 and April 2014. Fourteen TAPS cases [discordant middle cerebral artery peak systolic volume (MCA-PSV) or clinician diagnosis antenatally, or Hb >20 g/dL vs. <12 g/dL post-natally] were compared to an existing TTTS database (n = 142) and uncomplicated monochorionic diamniotic (MCDA) twin pregnancies (n = 45). Outcomes measured were maternal demographics; ultrasound findings at referral; management, including whether in utero fetal therapy was performed; and pregnancy outcome, including gestation at birth, mode of birth, birthweight, fetal/neonatal complications and neonatal survival to discharge.

The majority of TAPS cases were spontaneous (9/14) and occurred later in pregnancy than TTTS (median gestation at diagnosis 26.0 ± 4.9 vs. 20.4 ± 2.6 weeks, P < 0.001). However, TAPS perinatal outcome was similar to TTTS (survival of both twins 62% vs. 53%, survival of at least one twin 85% vs. 87%, overall survival 73% vs. 70%) and overall survival significantly lower than for uncomplicated MCDA pregnancies (73% vs. 98%, P < 0.001).

Overall mortality for TAPS was similar to that of TTTS but significantly higher compared to uncomplicated MCDA pregnancies, underscoring the potential severity of TAPS despite its later gestational onset.