title: Individual placental territories after selective laser photocoagulation of communicating vessels in twin-twin transfusion syndrome.
abstract: OBJECTIVE
  Intrauterine fetal death of one or both twins after laser therapy (selective photocoagulation of communicating vessels) may occur, in part, from insufficient individual placental mass. The objective of this study was to assess the percentage of individual placental mass (individual placental territory) that is associated with fetal survival in twin-twin transfusion syndrome after selective photocoagulation of communicating vessels.
  
  
  METHODS
  Placentas from 72 patients with selective photocoagulation of communicating vessels-treated twin-twin transfusion syndrome without intrauterine fetal death and from 61 monochorionic pregnancies without twin-twin transfusion syndrome (control subjects) were assessed. The placentas were weighed fresh (total placental mass) and cut along the vascular equator, which yielded the individual placental mass and the individual placental territory. Patency of anastomoses was ruled out with air-injection. The individual fetoplacental ratio was obtained by dividing birth weight by the corresponding individual placental mass.
  
  
  RESULTS
  The 5th percentile individual placental territory that was associated with fetal survival was 27% in control subjects and 18% in cases with twin-twin transfusion syndrome, with a minimum of 10% to 14%, respectively. There were no differences in total placental mass, individual placental mass, individual placental territory, or individual fetoplacental ratio between pregnancies with twin-twin transfusion syndrome and control subjects. However, corrected for gestational age, the birth weight of recipient and donor twins were significantly smaller than control subjects. The individual placental territory of donors was statistically smaller than that of recipients. Individual placental territories were not different within control subjects.
  
  
  CONCLUSIONS
  Fetal survival typically is associated with at least 18% of individual placental territory after selective photocoagulation of communicating vessels for twin-twin transfusion syndrome, but it can occur with as little as 10% to 14% individual placental territory. Decreased birth weight of the donor twin could result from relative decreased percentage of individual placental territory or from the loss of nutrients to the recipient twin. Decreased birth weight of the recipient twin could result from partial deprivation of functional placental tissue after surgery. Our findings may contribute to the understanding of normal and pathologic monochorionic twin gestations, in the counseling of patients, and potentially to the improvement of surgical treatment of twin-twin transfusion syndrome.
authors.affiliation: Florida Institute for Fetal Diagnosis and Therapy, St Joseph's Women's Hospital, Tampa, FL 33613, USA. yvrq@aol.com
authors.forename: Rubén A
authors.initials: RA
authors.lastname: Quintero
authors.forename: Josep M
authors.initials: JM
authors.lastname: Martínez
authors.forename: Jaime
authors.initials: J
authors.lastname: López
authors.forename: Carlos
authors.initials: C
authors.lastname: Bermúdez
authors.forename: Carlos
authors.initials: C
authors.lastname: Becerra
authors.forename: Walter
authors.initials: W
authors.lastname: Morales
authors.forename: Jorge
authors.initials: J
authors.lastname: Arroyo
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D005313:Fetal Death / Q000453:epidemiology*; D005330:Fetofetal Transfusion / Q000000981:diagnostic imaging / Q000601:surgery*; D005865:Gestational Age; D006801:Humans; D017075:Laser Coagulation / Q000379:methods*; D019060:Minimally Invasive Surgical Procedures; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple; D011336:Probability; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D014427:Twins; D016216:Ultrasonography, Prenatal