title: Triplet ultrasound growth parameters.
abstract: OBJECTIVE
  To create ultrasound growth curves for normal growth of fetal triplets using statistical methodology that properly accounts for similarities of growth of fetuses within a mother as well as repeated measurements over time for each fetus.
  
  
  METHODS
  In this longitudinal study, all triplet pregnancies managed at a single tertiary center from 1992-2004 were reviewed. Fetuses with major anomalies, prior selective reduction, or fetal demise were excluded. Data from early and late gestation in which there were fewer than 30 fetal measurements available for analysis were excluded. We used multilevel models to account for variation in growth within a single fetus over time, variations in growth between multiple fetuses within a single mother, and variations in fetal growth between mothers. Medians (50th), 10th, and 90th percentiles were estimated by the creation of multiple quadratic growth models from bootstrap samples adapting a previously published method to compute prediction intervals. Estimated fetal weight was derived from Hadlock's formula.
  
  
  RESULTS
  One hundred fifty triplet pregnancies were identified. Twenty-seven pregnancies were excluded for the following reasons: missing records (23), fetal demise (3), and fetal anomaly (1). The study group consisted of 123 pregnancies. The gestational age range was restricted to 14-34 weeks. Figures and tables were developed showing medians, 10th and 90th percentiles for estimated fetal weight, femur length, biparietal diameter, abdominal circumference, and head circumference.
  
  
  CONCLUSIONS
  Growth curves for triplet pregnancies were derived. These may be useful for identification of abnormal growth in triplet fetuses.
  
  
  METHODS
  III.
authors.affiliation: Department of Obstetrics and Gynecology, Tufts-New England Medical Center, Boston, Massachusetts 02116, USA. nraghavan@gmail.com
authors.forename: Neeta L
authors.initials: NL
authors.lastname: Vora
authors.forename: Robin
authors.initials: R
authors.lastname: Ruthazer
authors.forename: Michael
authors.initials: M
authors.lastname: House
authors.forename: David
authors.initials: D
authors.lastname: Chelmow
mesh_terms: D000886:Anthropometry; D005260:Female; D047109:Fetal Development / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D011247:Pregnancy; D012016:Reference Values; D014310:Triplets / Q000502:physiology*; D016216:Ultrasonography, Prenatal