title: Second-trimester estimated fetal weight and discordance in twin pregnancies: association with fetal growth restriction.
abstract: OBJECTIVE
  The purpose of this study was to estimate the association between second-trimester estimated fetal weight and fetal growth restriction in twin pregnancies.
  
  
  METHODS
  A historical cohort of 306 twin pregnancies from a single center was analyzed. Estimated fetal weight and discordance at 18 to 24 weeks were calculated. Patients with a fetus whose second-trimester estimated fetal weight was below the 10th percentile were compared to patients with both fetuses at or above the 10th percentile. Also, patients with second-trimester discordance of 15% or greater were compared to patients with discordance of less than 15%.
  
  
  RESULTS
  Second-trimester discordance was significantly smaller than birth weight discordance (mean discordance ± SD, 7.41% ± 6.06% versus 11.43% ± 9.6%, respectively; P < .001). Patients with second-trimester discordance of 15% or greater were significantly more likely to deliver a twin with a birth weight below the 10th percentile for gestational age (67.7% versus 44.1%; P = .012) and below the 5th percentile for gestational age (41.9% versus 22.8%; P = .019). Patients with a second-trimester estimated fetal weight below the 10th percentile were significantly more likely to deliver a twin with a birth weight below the 10th percentile for gestational age (65.5% versus 44.5%; P = .031) and below the 5th percentile for gestational age (55.2% versus 21.5%; P < .001).
  
  
  CONCLUSIONS
  In twin pregnancies, second-trimester estimated fetal weight below the 10th percentile and discordance of 15% or greater are associated with fetal growth restriction.
authors.affiliation: Maternal-Fetal Medicine Associates, PLLC, 70 E 90th St, New York, NY 10128, USA. nfox@mfmnyc.com
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Fox
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Saltzman
authors.forename: Rachel
authors.initials: R
authors.lastname: Schwartz
authors.forename: Ashley S
authors.initials: AS
authors.lastname: Roman
authors.forename: Chad K
authors.initials: CK
authors.lastname: Klauser
authors.forename: Andrei
authors.initials: A
authors.lastname: Rebarber
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging*; D020567:Fetal Weight; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011262:Pregnancy Trimester, Second; D059285:Pregnancy, Twin; D016216:Ultrasonography, Prenatal / Q000379:methods*