title: Which ultrasound or biochemical markers are independent predictors of small-for-gestational age?
abstract: OBJECTIVE
  To investigate which ultrasound or biochemical markers in both the first and the second trimesters are the best predictors for fetal growth and small-for-gestational age (SGA).
  
  
  METHODS
  This was a prospective study of 619 Chinese women with a singleton pregnancy. At 11 to 13 + 6 weeks, fetal crown-rump length (CRL), placental volume (PlaV), uterine artery pulsatility index (UtA-PI), and the maternal serum levels of pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (beta-hCG) were measured. Fetal biparietal diameter, femur length, abdominal and head circumference, PlaV and UtA-PI were then measured at 18-22 weeks. All markers were transformed to gestational age-specific Z-scores or multiples of the median (MoM). Birth weights were also transformed to Z-scores using the individualized gestational age-related optimal weight based on a locally derived nomogram. The relationship between all markers and the customized birth weight were examined, and their predictive powers for SGA were examined by regression analysis.
  
  
  RESULTS
  Univariate analysis revealed that all markers except free beta-hCG correlated with birth weight Z-score. After multiple linear regression analysis, only PlaV, UtA-PI and CRL in the first trimester, and PlaV and UtA-PI in the second trimester, stood out as independent markers. Logistic regression analysis showed that PlaV was the only independent first-trimester predictor of SGA, and in the second trimester both PlaV and UtA-PI were independent predictors. The sensitivity of these first- and second-trimester markers in predicting SGA were 41% and 45%, respectively, at a false-positive rate of 20%. Combining them did not significantly improve prediction of SGA.
  
  
  CONCLUSIONS
  Among the various known ultrasound and biochemical markers, only the first-trimester PlaV and the second-trimester PlaV plus UtA-PI are independent predictors for SGA.
authors: Fetal Medicine Unit, Department of Obstetrics and Gynecology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong SAR. lwlaw@cuhk.edu.hk
authors: L W
authors: LW
authors: Law
authors: T Y
authors: TY
authors: Leung
authors: D S
authors: DS
authors: Sahota
authors: L W
authors: LW
authors: Chan
authors: T Y
authors: TY
authors: Fung
authors: T K
authors: TK
authors: Lau
mesh_terms: D015415:Biomarkers / Q000097:blood; D001724:Birth Weight / Q000502:physiology*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D018568:Crown-Rump Length; D005260:Female; D047109:Fetal Development / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000097:blood; D008137:Longitudinal Studies; D009929:Organ Size; D010920:Placenta / Q000033:anatomy & histology; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A