title: Perinatal outcomes of twin anemia-polycythemia sequence: a systematic review.
abstract: OBJECTIVE
  To analyze outcomes of monochorionic twins with twin anemia-polycythemia sequence (TAPS).
  
  
  METHODS
  PubMed, EMBASE, Medline, and reference list.
  
  
  METHODS
  We included reports of TAPS defined prenatally with abnormal Doppler studies of middle cerebral artery and normal amniotic fluid volume which reported data as proportional rates.
  
  
  METHODS
  Abstracted outcomes were postnatal hemoglobin levels, postnatal procedures, and survival rates. Outcomes were analyzed for gestational age at diagnosis of TAPS (15 to 23 weeks, 24 to 29 weeks, > 29 weeks), in utero therapy, and nature of onset (isolated TAPS, or following twin-to-twin transfusion syndrome). The review was performed using MOOSE guidelines. Differences were significant if P < 0.05.
  
  
  RESULTS
  We assessed data on 28 pregnancies with TAPS. Diagnosis at 15 to 23 weeks' gestation and in utero therapy were associated with the highest mean levels of hemoglobin in anemic twins (P = 0.021), the lowest levels in polycythemic twins (P = 0.025), and the lowest frequency of postnatal procedures (P < 0.001). Survival rate was independent of gestational age at diagnosis and in utero therapy. In cases of TAPS following twin-to-twin transfusion, the mean hemoglobin level was higher in donors than in anemic twins with isolated TAPS (P = 0.029) and similar between recipients and polycythemic twins with isolated TAPS (P = 0.135). Twins with TAPS following twin-to-twin transfusion received in utero therapy more frequently than isolated TAPS twins (P = 0.030) and required a postnatal procedure less often (P < 0.001). Survival rates were similar in each group.
  
  
  CONCLUSIONS
  Diagnosis of TAPS at an early gestational age is associated with more favourable outcomes than later diagnosis. In utero therapy improves neonatal hemoglobin levels but does not change survival rates. Previous twin-to-twin transfusion syndrome does not worsen outcomes.
authors.affiliation: Department of Obstetrics and Gynecology, University of Bari, Bari, Italy.
authors.forename: A Cristina
authors.initials: AC
authors.lastname: Rossi
authors.affiliation: Maternal-Fetal Medicine Unit, Department of Obstetrics and Gynecology, University of Brescia, Brescia, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Prefumo
mesh_terms: D005260:Female; D005330:Fetofetal Transfusion / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology*; D005865:Gestational Age; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D011296:Prenatal Diagnosis
chemical_list: D006454:Hemoglobins
keywords: anemia polycythemia sequence; monochorionic pregnancy; twin transfusion syndromes; twins