title: A new formula for estimating fetal weight: The impression of biparietal diameter, abdominal circumference, mid-thigh soft tissue thickness and femoral length on birth weight.
abstract: BACKGROUND
  Abdominal circumference (AC), biparietal diameters (BPD) and femoral length (FL) are now the main parameters used to obtain estimated fetal weight (EFW). Although the role of soft tissue parameters in determining fetal weight was proved but clinical attention to mid-thigh soft tissue thickness (STT) is limited.
  
  
  OBJECTIVE
  To find the impression of STT on birth weight (BW) and represent a new predictive formula.
  
  
  METHODS
  One hundred and fourteen normal singleton term (36-42w) pregnancies with delivery within 72 hours were randomly selected to participate in this prospective cohort study. Variables measured by ultrasonography before birth included: AC, BPD, FL and STT. The actual neonatal BW was also measured after birth. Linear regression model was used and R square and p-value were reported.
  
  
  RESULTS
  The mean (SD) of BW was 3406 (405) gr. R square was best fit for the model that STT was added to AC, BPD, FL (r(2): 0.77). R square for the model using BPD, AC, FL and model using BPD, STT, FL was the same (r(2): 0.7). Best fit formula was Log (BW)= 2.461+0.003BPD+0.001AC+0.007STT+0.005FL.
  0.67, p<0.001), STT (R: 0.50, p<0.001), BPD (R: 0.59, p<0.001), FL (R: 0.66, p<0.001) were significantly correlated with birth weight. AC had also significant correlation with STT (p=0.001) CONCLUSION: This study showed adding STT to other variables in predictive models of fetal weight would provide a nice estimation (r(2)=0.77) and in cases that measuring AC is suboptimal STT may be a good replacement.
authors.affiliation: Department of Radiology, Mahdiyeh Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mojgan
authors.initials: M
authors.lastname: Kalantari
authors.affiliation: Department of Radiology, Mahdiyeh Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Arezou
authors.initials: A
authors.lastname: Negahdari
authors.affiliation: Department of Radiology, Mahdiyeh Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Shima
authors.initials: S
authors.lastname: Roknsharifi
authors.affiliation: Department of Public Health, Alborz University of Medical Sciences, Karaj, Iran. ; Non-Communicable Diseases Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Qorbani
keywords: Abdominal circumference; Biparietal diameters; Femoral length; Fetal weight; Soft tissue thickness; Ultrasonography