title: Customizing fetal biometric charts.
abstract: OBJECTIVE
  To study the effects of maternal and pregnancy characteristics on fetal biometric size using longitudinal ultrasound measurements and to construct customized models for fetal biometric size charts.
  
  
  METHODS
  A cohort of 533 healthy pregnant women with normal singleton pregnancies were recruited for regular ultrasound examination for fetal biometry between 24 and 40 weeks' gestation. Multilevel modeling was used to construct models of fetal head size, femur length and abdominal circumference. Variables of maternal and pregnancy characteristics including booking weight and height, age, parity and fetal sex were included in the construction of the customized fetal biometric size charts.
  
  
  RESULTS
  Increased fetal head size and abdominal circumference were significantly associated with extremes of maternal age. Maternal height had a statistically significant influence on biparietal diameter. Maternal booking weight had an influence on fetal abdominal circumference and femur length. Fetal sex was found to have a statistically significant influence on the final regression models of biparietal diameter, head circumference and femur length. Parity had an influence on fetal head circumference and abdominal circumference.
  
  
  CONCLUSIONS
  Maternal and pregnancy characteristics have a significant influence on in-utero fetal biometry. We produced models to construct customized fetal biometric size charts. Further validation studies are necessary to evaluate the clinical usefulness of such customized fetal biometric size charts.
authors.affiliation: Department of Obstetrics and Gynaecology, Prince of Wales Hospital, Hong Kong, SAR. MWPang@cuhk.edu.hk
authors.forename: M W
authors.initials: MW
authors.lastname: Pang
authors.forename: T N
authors.initials: TN
authors.lastname: Leung
authors.forename: D S
authors.initials: DS
authors.lastname: Sahota
authors.forename: T K
authors.initials: TK
authors.lastname: Lau
authors.forename: A M Z
authors.initials: AM
authors.lastname: Chang
mesh_terms: D000328:Adult; D000886:Anthropometry; D001699:Biometry; D015331:Cohort Studies; D005314:Embryonic and Fetal Development; D005260:Female; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D011247:Pregnancy; D012016:Reference Values; D012044:Regression Analysis; D016216:Ultrasonography, Prenatal