title: Fetal venous circulation in monochorionic twin pregnancies with placental insufficiency: prediction of acidemia at birth or intrauterine fetal death.
abstract: OBJECTIVE
  To investigate fetal venous Doppler measurements in monochorionic twin pregnancies complicated by placental insufficiency and the relationship between fetal venous flow and acidemia at birth or intrauterine fetal death.
  
  
  METHODS
  This was a prospective study of 18 monochorionic twin pregnancies with placental insufficiency. Inclusion criteria were monochorionic-diamniotic twin pregnancy, abnormal umbilical artery (UA) Doppler indices, intact membranes and absence of fetal congenital abnormalities. Cases of twin-to-twin transfusion syndrome were excluded. The following Doppler measurements were studied: UA pulsatility index (PI), ductus venosus PI, middle cerebral artery PI and peak systolic velocity, intra-abdominal umbilical vein (UV) time-averaged maximum velocity (TAMXV) and left portal vein (LPV) TAMXV. Doppler parameters were transformed into Z-scores (SD values from the mean) or multiples of the median according to normative references.
  
  
  RESULTS
  UA pH < 7.20 occurred in nine (25.0%) neonates, pH < 7.15 in four (11.1%) and intrauterine death in four (11.1%) fetuses. The UV-TAMXV and LPV-TAMXV Z-scores were significantly lower in the group with pH < 7.20 or intrauterine fetal death (-1.79 vs -1.22, P = 0.006 and -2.26 vs -1.13, P = 0.04, respectively). In cases with pH < 7.15 or intrauterine fetal death, UV pulsations were more frequent (50.0% vs 10.7%, P = 0.03) and UV-TAMXV Z-score was significantly lower (-1.89 vs -1.26, P = 0.003). Mixed effects logistic regression analysis, accounting for the paired nature of the outcomes for the two twins in each pregnancy, demonstrated that the UV-TAMXV Z-score significantly predicted UA pH at birth < 7.20 or intrauterine fetal death. The Doppler parameter that independently predicted pH < 7.15 or intrauterine fetal death was presence of pulsation in the UV.
  
  
  CONCLUSIONS
  UV Doppler parameters may predict acidemia at birth or intrauterine fetal death in monochorionic twins complicated by placental insufficiency.
authors.affiliation: Department of Obstetrics and Gynecology, School of Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: T B
authors.initials: TB
authors.lastname: Liao
authors.forename: R M Y
authors.initials: RM
authors.lastname: Nomura
authors.forename: A W
authors.initials: AW
authors.lastname: Liao
authors.forename: R P V
authors.initials: RP
authors.lastname: Francisco
authors.forename: M
authors.initials: M
authors.lastname: Zugaib
mesh_terms: D000138:Acidosis / Q000000981:diagnostic imaging / Q000401:mortality / Q000503:physiopathology*; D001783:Blood Flow Velocity; D005260:Female; D005313:Fetal Death; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005333:Fetus / Q000098:blood supply*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010927:Placental Insufficiency / Q000000981:diagnostic imaging / Q000401:mortality / Q000503:physiopathology*; D011169:Portal Vein / Q000000981:diagnostic imaging / Q000196:embryology / Q000503:physiopathology*; D011247:Pregnancy; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin; D011446:Prospective Studies; D011673:Pulsatile Flow; D012680:Sensitivity and Specificity; D018608:Ultrasonography, Doppler; D014469:Umbilical Arteries / Q000098:blood supply*
keywords: monochorionic twin; placental insufficiency; prediction; twin pregnancy; venous Doppler