title: Prediction of small-for-gestational-age neonates: screening by biophysical and biochemical markers at 19-24 weeks.
abstract: OBJECTIVE
  To investigate the value of combined screening by maternal characteristics and medical history, fetal biometry and biophysical and biochemical markers at 19-24 weeks' gestation, for prediction of delivery of small-for-gestational-age (SGA) neonates, in the absence of pre-eclampsia (PE), and examine the potential value of such assessment in deciding whether the third-trimester scan should be at 32 and/or 36 weeks' gestation.
  
  
  METHODS
  This was a screening study in 7816 singleton pregnancies, including 389 (5.0%) that delivered SGA neonates with birth weight < 5(th) percentile (SGA < 5(th) ), in the absence of PE. Multivariable logistic regression analysis was used to determine if screening by a combination of maternal factors, fetal biometry, uterine artery pulsatility index (UtA-PI) and maternal serum concentrations of placental growth factor (PlGF) and α-fetoprotein (AFP) had significant contribution in predicting SGA neonates. A model was developed for selecting the gestational age for third-trimester assessment, at 32 and/or 36 weeks, based on the results of screening at 19-24 weeks.
  
  
  RESULTS
  Significant independent contributions to the prediction of SGA < 5(th) were provided by maternal factors, fetal biometry, UtA-PI and serum PlGF and AFP. The detection rate (DR) of such combined screening at 19-24 weeks was 100%, 78% and 42% for SGA < 5(th) delivering < 32, at 32-36 and ≥ 37 weeks' gestation, respectively, at a false-positive rate (FPR) of 10%. In a hypothetical model, it was estimated that if the desired objective of prenatal screening is to predict about 80% of the cases of SGA < 5(th) , it would be necessary to select 11% of the population at the 19-24-week assessment to be reassessed at 32 weeks and 44% to be reassessed at 36 weeks; 57% would not require a third-trimester scan.
  
  
  CONCLUSIONS
  Prenatal prediction of a high proportion of SGA neonates necessitates the undertaking of screening in the third trimester of pregnancy, in addition to assessment in the second trimester, and the timing of such screening, at 32 and/or 36 weeks, should be contingent on the results of the assessment at 19-24 weeks.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: L C
authors.initials: LC
authors.lastname: Poon
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Lesmes
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: D M
authors.initials: DM
authors.lastname: Gallo
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.|Fetal Medicine Unit, Medway Maritime Hospital, Gillingham, Kent, UK.
authors.forename: R
authors.initials: R
authors.lastname: Akolekar
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D005260:Female; D005317:Fetal Growth Retardation / Q000097:blood / Q000000981:diagnostic imaging; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000378:metabolism*; D008297:Male; D000072483:Placenta Growth Factor; D011237:Predictive Value of Tests; D011247:Pregnancy / Q000097:blood*; D011257:Pregnancy Proteins / Q000097:blood*; D011295:Prenatal Care / Q000379:methods; D011296:Prenatal Diagnosis / Q000379:methods; D011446:Prospective Studies; D018617:Ultrasonography, Doppler, Pulsed / Q000379:methods; D016216:Ultrasonography, Prenatal / Q000379:methods; D055988:Uterine Artery / Q000000981:diagnostic imaging; D000509:alpha-Fetoproteins / Q000378:metabolism*
chemical_list: D015415:Biomarkers; C000608036:PGF protein, human; D011257:Pregnancy Proteins; D000509:alpha-Fetoproteins; D000072483:Placenta Growth Factor
keywords: placental growth factor; pre-eclampsia; pyramid of antenatal care; second-trimester screening; small-for-gestational age; uterine artery pulsatility index; α-fetoprotein