Routine ultrasound at 32 vs 36 weeks' gestation: prediction of small-for-gestational-age neonates
Journal article
Ciobanu, A., Khan, N., Syngelaki, A., Akolekar, R. and Nicolaides, K. H. 2019. Routine ultrasound at 32 vs 36 weeks' gestation: prediction of small-for-gestational-age neonates. Ultrasound in Obstetrics and Gynecology. 53 (6), pp. 761-768. https://doi.org/10.1002/uog.20258
Authors | Ciobanu, A., Khan, N., Syngelaki, A., Akolekar, R. and Nicolaides, K. H. |
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Abstract | Objective: To evaluate and compare the performance of routine ultrasonographic estimated fetal weight (EFW) and fetal abdominal circumference (AC) at 31+0 - 33+6 and 35+0 - 36+6 weeks’ gestation in the prediction of small for gestational age (SGA) neonates. Methods: This was a prospective study of 21,989 singleton pregnancies that had undergone routine ultrasound examination at 31+0 - 33+6 weeks’ gestation and 45,847 that had undergone routine ultrasound examination at 35+0 - 36+6 weeks’ gestation. In each case the estimated fetal weight (EFW) from measurements of fetal head circumference (HC), AC and femur length (FL) was calculated by the Hadlock formula and this was expressed as percentile according to the Fetal Medicine Foundation fetal and neonatal population weight charts. The same charts were used for defining SGA neonates with birthweight <10th and <3rd percentiles. For each gestational window the screen positive and detection rate, at different EFW percentile cut-offs between the 10th and 50th percentile, were calculated for prediction of delivery of SGA neonates with birthweight <10th and <3rd percentiles within two weeks and at any stage after assessment. The areas under the receiver operating characteristics curve (AUROC) of screening for SGA neonates by EFW and AC at 31+0 - 33+6 and at 35+0 - 36+6 weeks’ gestation were compared. Results: First, the AUROCs of screening by EFW for SGA neonates with birthweight <10th and <3rd percentiles within two weeks and at any stage after screening at 35+0 - 36+6 weeks’ gestation were significantly higher than those at 31+0 - 33+6 weeks (p<0.001). Second, at both 35+0 - 36+6 and 31+0 - 33+6 weeks’ gestation, the predictive performance for SGA neonates with birthweight <10th and <3rd percentiles born at any stage after screening was significantly higher with EFW Z-score than AC Z-score. Similarly, at 35+0 - 36+6 weeks, but not at 31+0 - 33+6 weeks, the predictive performance for SGA neonates with birthweight <10th and <3rd percentiles born within two weeks of screening was significantly higher with EFW Z-score than AC Z-score. Third, screening by EFW <10th percentile at 35+0 - 36+6 weeks’ gestation predicted 70% and 84% of neonates with birthweight <10th and <3rd percentiles born within two weeks after assessment and the respective values for neonates born at any stage after assessment were 46% and 65%. Fourth, prediction of >85% of SGA neonates with birthweight <10th percentile born at any stage after screening at 35+0 - 36+6 weeks’ gestation requires use of EFW <40th percentile. Screening at this percentile cut-off predicted 95% and 99% of neonates with birthweight <10th and <3rd percentiles born within two weeks after assessment and the respective values for neonates born at any stage after assessment were 88% and 94%. Conclusion: The predictive performance for SGA neonates by routine ultrasonographic examination during the third trimester is higher if first, the scan is carried out at 35+0 - 36+6 weeks’ gestation than at 31+0 - 33+6 weeks; second, the method of screening is EFW than fetal AC; third, the outcome measure is birthweight <3rd than <10th percentile; and fourth, if delivery occurs within two weeks than at any stage after assessment. Prediction of SGA neonates by EFW <10th percentile is modest and prediction of >85% of cases at 35+0 - 36+6 weeks’ gestation necessitates use of EFW <40th percentile. |
Keywords | Third trimester screening; Small for gestational age; Adverse perinatal outcome; Estimated fetal weight; Fetal biometry; Symphysial-fundal height; Pyramid of pregnancy care |
Year | 2019 |
Journal | Ultrasound in Obstetrics and Gynecology |
Journal citation | 53 (6), pp. 761-768 |
Publisher | Wiley |
ISSN | 0960-7692 |
Digital Object Identifier (DOI) | https://doi.org/10.1002/uog.20258 |
Official URL | https://doi.org/10.1002/uog.20258 |
Publication dates | |
Online | 30 Apr 2019 |
Publication process dates | |
Accepted | 05 Mar 2019 |
Deposited | 18 May 2020 |
Accepted author manuscript | |
Output status | Published |
https://repository.canterbury.ac.uk/item/8v42z/routine-ultrasound-at-32-vs-36-weeks-gestation-prediction-of-small-for-gestational-age-neonates
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