title: Prenatal prediction of significant intertwin birthweight discordance using standard second and third trimester sonographic parameters.
abstract: BACKGROUND
  Our study aim was to evaluate standard ultrasound-derived fetal biometric parameters in the prediction of clinically significant intertwin birthweight discordance defined as ≥18%.
  
  
  METHODS
  This was a secondary analysis of a prospective cohort study of 1028 unselected twin pairs recruited over a two-year period. Dichorionic twins underwent two-weekly ultrasonographic surveillance from 24 weeks' gestation, with surveillance of monochorionic twins two-weekly from 16 weeks. Ultrasonographic biometric data from 24 to 36 weeks were evaluated for the prediction of an intertwin birthweight discordance threshold ≥18%. Umbilical artery Doppler waveform data was also analyzed to evaluate whether it was predictive of birthweight discordance.
  
  
  RESULTS
  Of the 956 twin pairs analyzed for discordance, 208 pairs were found to have a clinically significant birthweight discordance ≥18%. All biometric parameters were predictive of significant inter-twin birthweight discordance at low cut-offs, with low discriminatory powers when ROC curves were analyzed. Discordance in estimated fetal weight was predictive of a significant birthweight discordance at all gestational categories with cut-offs between 8 and 11%. A low-discriminatory power and poor sensitivity and specificity were also observed. An abnormal umbilical artery Doppler was predictive of birthweight discordance ≥18% between 28 and 32 weeks' gestation, although with poor sensitivity and specificity.
  
  
  CONCLUSIONS
  Calculation of estimated fetal weight and birthweight discordance between twins allows minimal margin for error. These margins make it difficult to accurately predict those who are at or above the discordance threshold of 18%. These findings highlight that small intertwin discrepancies in weight and biometry should not be overlooked and merit further investigation.
authors.affiliation: Royal College of Surgeons in Ireland, Dublin, Ireland.|Rotunda Hospital, Dublin, Ireland.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Hehir
authors.affiliation: Royal College of Surgeons in Ireland, Dublin, Ireland.|Rotunda Hospital, Dublin, Ireland.
authors.forename: Fionnuala M
authors.initials: FM
authors.lastname: Breathnach
authors.affiliation: Rotunda Hospital, Dublin, Ireland.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Hogan
authors.affiliation: School of Medicine and Medical Science, University College Dublin, Dublin, Ireland.|National Maternity Hospital, Dublin, Ireland.
authors.forename: Fionnuala M
authors.identifier: http://orcid.org/0000-0002-3477-6494
authors.initials: FM
authors.lastname: Mcauliffe
authors.affiliation: Royal College of Surgeons in Ireland, Dublin, Ireland.|Rotunda Hospital, Dublin, Ireland.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Geary
authors.affiliation: Coombe Women and Infant University Hospital, Dublin, Ireland.
authors.forename: Sean
authors.initials: S
authors.lastname: Daly
authors.affiliation: University College Cork, Cork, Ireland.
authors.forename: John
authors.initials: J
authors.lastname: Higgins
authors.affiliation: Royal Victoria University Hospital Belfast, Belfast, Northern Ireland, UK.
authors.forename: Alyson
authors.initials: A
authors.lastname: Hunter
authors.affiliation: University Hospital Galway, Galway, Ireland.
authors.forename: John J
authors.initials: JJ
authors.lastname: Morrison
authors.affiliation: Mid-Western Regional Hospital, Limerick, Ireland.
authors.forename: Gerard
authors.initials: G
authors.lastname: Burke
authors.affiliation: National Maternity Hospital, Dublin, Ireland.
authors.forename: Rhona
authors.initials: R
authors.lastname: Mahony
authors.affiliation: Royal College of Surgeons in Ireland, Dublin, Ireland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Dicker
authors.affiliation: Royal College of Surgeons in Ireland, Dublin, Ireland.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tully
authors.affiliation: Royal College of Surgeons in Ireland, Dublin, Ireland.|Rotunda Hospital, Dublin, Ireland.
authors.forename: Fergal D
authors.initials: FD
authors.lastname: Malone
mesh_terms: D000328:Adult; D019540:Area Under Curve; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging*; D006801:Humans; D007231:Infant, Newborn; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D013548:Sweden; D014427:Twins; D016216:Ultrasonography, Prenatal; D014469:Umbilical Arteries / Q000000981:diagnostic imaging*
keywords: Twins; birthweight; discordance; estimation; ultrasound