Placental types and twin-twin transfusion syndrome.
OBJECTIVE
The purpose of this study was to assess the value of a proposed classification of monochorionic placenta in reference to twin-twin transfusion syndrome.


METHODS
The placentas from laser-treated patients with twin-twin transfusion syndrome and from uncomplicated monochorionic pregnancies that were delivered between January 1997 and December 2000 were included in the study. Placentas were classified as type A (no anastomoses), type B (only deep anastomoses), type C (only superficial anastomoses), and type D (deep and superficial anastomoses). The number and type of anastomoses were documented in each placental type. The severity of twin-twin transfusion syndrome was assessed in stages, as previously described. The relationship between placental types and the development and severity of twin-twin transfusion syndrome was determined.


RESULTS
One hundred thirty-one placentas were examined. Twin-twin transfusion syndrome developed in 0% (0/4 placentas) of type A, in 100% (85/85 placentas) of type B, in 5.6% (1/18 placentas) of type C, and in 79.17% (19/24 placentas) of type D placentas. An average of 4.17 (range, 1-11) vascular anastomoses was found. The mean number of superficial anastomoses was not different between patients with twin-twin transfusion syndrome and patients with no twin-twin transfusion syndrome (1.6 vs 1.71, respectively; P =.69, Student t test). The presence or absence of superficial anastomoses was not associated with differences in the severity of twin-twin transfusion syndrome.


CONCLUSIONS
This classification represents a practical approach to the surgical pathologic assessment of vascular anastomoses in monochorionic placentas, with a strong clinical correlation. It also allows for the clarification of the relationship between superficial anastomoses and twin-twin transfusion syndrome.
Bermúdez
Carlos
C
Florida Institute for Fetal Diagnosis and Therapy, St Joseph's Women's Hospital, Tampa, USA.
Becerra
Carlos H
CH
Bornick
Patricia W
PW
Allen
Mary H
MH
Arroyo
Jorge
J
Quintero
Rubén A
RA
D001163:Arteriovenous Anastomosis / Q000473:pathology; D005260:Female; D005330:Fetofetal Transfusion / Q000473:pathology* / Q000628:therapy; D006801:Humans; D017075:Laser Coagulation; D010920:Placenta / Q000473:pathology*; D011247:Pregnancy; D011272:Pregnancy, Multiple; D014430:Twins, Monozygotic