title: Unconditional and conditional standards for fetal abdominal circumference and estimated fetal weight in an ethnic Chinese population: a birth cohort study.
abstract: BACKGROUND
  Diagnosis of intrauterine fetal growth restriction and prediction of small-for-gestation age are often based on fetal abdominal circumference or estimated fetal weight (EFW). The present study aims to create unconditional (cross-sectional) and conditional (longitudinal) standards of fetal abdominal circumference and EFW for use in an ethnic Chinese population.
  
  
  METHODS
  In the Growing Up in Singapore Towards healthy Outcome (GUSTO) birth cohort study in Singapore, fetal biometric measurements were obtained at enrolment to antenatal care (11-12 weeks) and up to three more time points during pregnancy. Singleton pregnancies with a healthy profile defined by maternal, pregnancy and fetal characteristics and birth outcomes were selected for this analysis. The Hadlock algorithm was used to calculate EFW. Mixed effects model was used to establish unconditional and conditional standards in z-scores and percentiles for both genders pooled and for each gender separately.
  
  
  RESULTS
  A total of 313 women were included, of whom 294 had 3 and 19 had 2 ultrasound scans other than the gestational age dating scan. Fetal abdominal circumference showed a roughly linear trajectory from 18 to 36 weeks of gestation, while EFW showed an accelerating trajectory. Gender differences were more pronounced in the 10(th) percentile than the 50(th) or 90(th) percentiles. As compared to other published charts, this population showed growth trajectories that started low but caught up at later gestations.
  
  
  CONCLUSIONS
  Unconditional and conditional standards for monitoring fetal size and fetal growth in terms of abdominal circumference and EFW are available for this ethnic-Chinese population. Electronic spreadsheets are provided for their implementation.
authors.affiliation: Duke-NUS Graduate Medical School, National University of Singapore, Singapore, Singapore. tinayxu@gmail.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Duke-NUS Graduate Medical School, National University of Singapore, Singapore, Singapore. lek.ngee@kkh.com.sg.|Department of Pediatrics, KK Women's and Children's Hospital, Singapore, Singapore. lek.ngee@kkh.com.sg.
authors.forename: Ngee
authors.initials: N
authors.lastname: Lek
authors.affiliation: Duke-NUS Graduate Medical School, National University of Singapore, Singapore, Singapore. yinbun.cheung@duke-nus.edu.sg.|Department of International Health, University of Tampere, Tampere, Finland. yinbun.cheung@duke-nus.edu.sg.
authors.forename: Yin Bun
authors.initials: YB
authors.lastname: Cheung
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore. obgab@nus.edu.sg.
authors.forename: Arijit
authors.initials: A
authors.lastname: Biswas
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore. lin_lin_su@nuhs.edu.sg.
authors.forename: Lin Lin
authors.initials: LL
authors.lastname: Su
authors.affiliation: Division of Obstetrics and Gynaecology, KK Women's and Children's Hospital, Singapore, Singapore. Kenneth.Kwek.YC@kkh.com.sg.
authors.forename: Kenneth Y C
authors.initials: KY
authors.lastname: Kwek
authors.affiliation: Division of Obstetrics and Gynaecology, KK Women's and Children's Hospital, Singapore, Singapore. dr.george.sh.yeo@gmail.com.
authors.forename: George S H
authors.initials: GS
authors.lastname: Yeo
authors.affiliation: Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore. Soh_Shu_E@sics.a-star.edu.sg.|Saw Swee Hock School of Public Health, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. Soh_Shu_E@sics.a-star.edu.sg.
authors.forename: Shu-E
authors.initials: SE
authors.lastname: Soh
authors.affiliation: Saw Swee Hock School of Public Health, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. ephssm@nus.edu.sg.
authors.forename: Seang-Mei
authors.initials: SM
authors.lastname: Saw
authors.affiliation: Singapore Institute for Clinical Sciences, Agency for Science Technology and Research (A*STAR), Singapore, Singapore. pd.gluckman@auckland.ac.nz.|Liggins Institute, University of Auckland, Auckland, New Zealand. pd.gluckman@auckland.ac.nz.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Gluckman
authors.affiliation: Department of Obstetrics and Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore. yap_seng_chong@nuhs.edu.sg.|Singapore Institute for Clinical Sciences, Agency for Science Technology and Research (A*STAR), Singapore, Singapore. yap_seng_chong@nuhs.edu.sg.
authors.forename: Yap-Seng
authors.initials: YS
authors.lastname: Chong
mesh_terms: D000328:Adult; D000465:Algorithms; D044466:Asian People / Q000208:ethnology; D001699:Biometry / Q000379:methods; D001724:Birth Weight; D005260:Female; D047109:Fetal Development; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging / Q000208:ethnology; D020567:Fetal Weight / Q000208:ethnology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D008423:Maternal Age; D011247:Pregnancy; D011295:Prenatal Care; D012016:Reference Values; D012737:Sex Factors; D012846:Singapore; D016216:Ultrasonography, Prenatal / Q000706:statistics & numerical data*; D055105:Waist Circumference