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Ultrasound estimation of birth weight in twin pregnancy: comparison of biometry algorithms in the STORK multiple pregnancy cohort
Author(s) -
Khalil A.,
D'Antonio F.,
Dias T.,
Cooper D.,
Thilaganathan B.
Publication year - 2014
Publication title -
ultrasound in obstetrics and gynecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.202
H-Index - 141
eISSN - 1469-0705
pISSN - 0960-7692
DOI - 10.1002/uog.13253
Subject(s) - singleton , medicine , obstetrics , twin pregnancy , birth weight , pregnancy , concordance , cohort , gestational age , multiple birth , gestation , fetal weight , retrospective cohort study , gynecology , population , surgery , genetics , biology , environmental health
ABSTRACT Objectives The aims of this study were first, to ascertain the accuracy of formulae for ultrasonographic birth‐weight estimation in twin compared with singleton pregnancies and second, to assess the accuracy of sonographic examination in the prediction of birth‐weight discordance in twin pregnancies. Methods This was a retrospective cohort study including both singleton and twin pregnancies. Routine biometry was recorded and estimated fetal weight ( EFW ) calculated using 33 different formulae. Only pregnancies that delivered within 48 h of the ultrasound scan were included (4280 singleton and 586 twin fetuses). Differences between the EFW and actual birth weight ( ABW ) were assessed by percentage error, accuracy in predictions within ± 10 % and ± 15% of error and use of the Bland–Altman method. The accuracy of prediction of the different cut‐offs of birth‐weight discordance in twin pregnancies was also assessed using the area under the receiver–operating characteristics curve ( AUC ). Results The overall mean absolute percentage error was ≤ 10 % for 25 formulae in singleton pregnancies compared with three formulae in twin pregnancies. The overall predictions within ± 10% and ± 15% of the ABW were 62.2% and 81.5% in singleton and 49.7% and 68.5% in twin pregnancies, respectively. When the formulae were categorized according to the biometric parameters included, those based on a combination of head, abdomen and femur measurements showed the lowest mean absolute percentage error, in both singleton and twin pregnancies. The predictive accuracy for 25% birth‐weight discordance using the Hadlock 2 formula, as assessed by the AUC , was 0.87. Conclusions Ultrasound estimation of birth weight is less accurate in twin than in singleton pregnancies. Formulae that include a combination of head, abdomen and femur measurements perform best in both singleton and twin pregnancies. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd