Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.
OBJECTIVE
We sought to correlate placental vasculature with fetal growth and outcome in monochorionic twins.


METHODS
Eighty-two patients with consecutive monochorionic pregnancies underwent biweekly ultrasonography for determination of fetal growth and well-being. After delivery, blinded placental injection studies delineated vascular anastomoses and territory share. Degree of balance in arteriovenous anastomoses equaled the number of arteriovenous anastomoses in one direction minus the number in the other.


RESULTS
Pregnancies affected by fetofetal transfusion syndrome (n = 21) had numbers of arteriovenous and venovenous anastomoses that were similar to those in pregnancies without fetofetal transfusion syndrome but fewer arterioarterial anastomoses (P <.0001). Fetofetal transfusion syndrome occurred in 78% of pregnancies with >/=1 arteriovenous and no arterioarterial anastomoses. Birth weight discordancy correlated with placental territory discordancy (P <.0001) and the degree of balance in arteriovenous anastomoses (P =.004). The larger placental share twin had a greater growth velocity than its smaller placental share co-twin (P =.008) for all but one anastomotic pattern. Where arteriovenous anastomoses were aligned with the net venous outflow to the fetus with the smaller territory, co-twins had similar birth weights and growth velocities irrespective of placental share. Fetal survival was higher in pregnancies with an arterioarterial anastomosis (P =.01) but lower with a venovenous anastomosis (P =. 01). Survival of both fetuses was inversely associated with birth weight discordancy (P <.0001).


CONCLUSIONS
Although interrelationships among the various types of anastomoses are complex, our data suggest that the placental territory share and the pattern of arteriovenous anastomoses influence fetal growth, that arterioarterial anastomoses protect against fetofetal transfusion syndrome, and that venovenous anastomoses reduce perinatal survival.
Denbow
M L
ML
Department of Materno-Fetal Medicine, Queen Charlotte's and Chelsea Hospital, Imperial College School of Medicine, London, United Kingdom.
Cox
P
P
Taylor
M
M
Hammal
D M
DM
Fisk
N M
NM
D001163:Arteriovenous Anastomosis / Q000196:embryology* / Q000503:physiopathology; D001724:Birth Weight; D015331:Cohort Studies; D016861:Cyclooxygenase Inhibitors / Q000627:therapeutic use; D005314:Embryonic and Fetal Development / Q000502:physiology*; D005260:Female; D005330:Fetofetal Transfusion / Q000175:diagnosis*; D005865:Gestational Age; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007231:Infant, Newborn; D016015:Logistic Models; D015999:Multivariate Analysis; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple / Q000502:physiology*; D011446:Prospective Studies; D013467:Sulindac / Q000627:therapeutic use; D014430:Twins, Monozygotic; D018615:Ultrasonography, Doppler, Color; D016216:Ultrasonography, Prenatal
D016861:Cyclooxygenase Inhibitors; D013467:Sulindac