title: Contingent versus routine third-trimester screening for late fetal growth restriction.
abstract: OBJECTIVE
  To evaluate the use of third-trimester ultrasound screening for late fetal growth restriction (FGR) on a contingent basis, according to risk accrued in the second trimester, in an unselected population.
  
  
  METHODS
  Maternal characteristics, fetal biometry and second-trimester uterine artery (UtA) Doppler were included in logistic regression analysis to estimate risk for late FGR (birth weight < 3(rd) percentile, or 3(rd) -10(th) percentile plus abnormal cerebroplacental ratio or UtA Doppler, with delivery ≥ 34 weeks). Based on the second-trimester risk, strategies for performing contingent third-trimester ultrasound examinations in 10%, 25% or 50% of the cohort were tested against a strategy of routine ultrasound scanning in the entire population at 32 + 0 to 33 + 6 weeks.
  
  
  RESULTS
  Models were constructed based on 1393 patients and validated in 1303 patients, including 73 (5.2%) and 82 late FGR (6.3%) cases, respectively. At the second-trimester scan, the a-posteriori second-trimester risk (a-posteriori first-trimester risk (baseline a-priori risk and mean arterial blood pressure) combined with second-trimester abdominal circumference and UtA Doppler) yielded an area under the receiver-operating characteristics curve (AUC) of 0.81 (95% CI, 0.74-0.87) (detection rate (DR), 43.1% for a 10% false-positive rate (FPR)). The combination of a-posteriori second-trimester risk plus third-trimester estimated fetal weight (full model) yielded an AUC of 0.92 (95% CI, 0.88-0.96) (DR, 74% for a 10% FPR). Subjecting 10%, 25% or 50% of the study population to third-trimester ultrasound, based on a-posteriori second-trimester risk, gave AUCs of 0.81 (95% CI, 0.75-0.88), 0.84 (95% CI, 0.78-0.91) and 0.89 (95% CI, 0.84-0.94), respectively. Only the 50% contingent model proved statistically equivalent to performing routine third-trimester ultrasound scans (AUC, 0.92 (95% CI, 0.88-0.96), P = 0.11).
  
  
  CONCLUSIONS
  A strategy of selecting 50% of the study population to undergo third-trimester ultrasound examination, based on accrued risk in the second trimester, proved equivalent to routine third-trimester ultrasound scanning in predicting late FGR.
authors.affiliation: Fetal i+D Fetal Medicine Research Center, BCNatal - Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Deu), IDIBAPS, University of Barcelona, Barcelona, Spain.|Centre for Biomedical Research on Rare Diseases (CIBER-ER), Valencia, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Triunfo
authors.affiliation: Fetal i+D Fetal Medicine Research Center, BCNatal - Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Deu), IDIBAPS, University of Barcelona, Barcelona, Spain.|Centre for Biomedical Research on Rare Diseases (CIBER-ER), Valencia, Spain.|Fondazione Cà Granda, Ospedale Maggiore Policlinico, Dipartimento Ostetricia e Ginecologia, Università degli Studi di Milano, Milan, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Crovetto
authors.affiliation: Obstetrics, Gynecology and Reproductive Medicine Department, Institut Universitari Dexeus, Barcelona, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Scazzocchio
authors.affiliation: Maternal-Fetal Unit, CEDIFETAL, Centro de Diagnóstico de Ultrasonido e Imágenes, CEDIUL, Barranquilla, Colombia.
authors.forename: M
authors.initials: M
authors.lastname: Parra-Saavedra
authors.affiliation: Fetal i+D Fetal Medicine Research Center, BCNatal - Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Deu), IDIBAPS, University of Barcelona, Barcelona, Spain.|Centre for Biomedical Research on Rare Diseases (CIBER-ER), Valencia, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Gratacos
authors.affiliation: Fetal i+D Fetal Medicine Research Center, BCNatal - Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Deu), IDIBAPS, University of Barcelona, Barcelona, Spain.|Centre for Biomedical Research on Rare Diseases (CIBER-ER), Valencia, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Figueras
mesh_terms: D000328:Adult; D019540:Area Under Curve; D001699:Biometry; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging*; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D008403:Mass Screening; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D011296:Prenatal Diagnosis / Q000379:methods; D011446:Prospective Studies; D018608:Ultrasonography, Doppler; D016216:Ultrasonography, Prenatal / Q000379:methods*; D055988:Uterine Artery / Q000000981:diagnostic imaging*
keywords: estimated fetal weight; fetal growth restriction; neonatal complications; ultrasonography; uterine artery Doppler