Third trimester ultrasound for fetal macrosomia: optimal timing and institutional specific accuracy

Abstract

Purpose: To determine the performance of third trimester ultrasound in women with suspected fetal macrosomia.

Materials and methods: We performed a retrospective cohort study of fetal ultrasounds from January 2004 to December 2014 with estimated fetal weight (EFW) between 4000 and 5000 g. We determined accuracy of birth weight prediction for ultrasound performed at less than and greater than 38 weeks, accounting for diabetic status and time between ultrasound and delivery.

Results: There were 405 ultrasounds evaluated. One hundred and twelve (27.7%) were performed at less than 38 weeks, 293 (72.3%) at greater than 38 weeks, and 91 (22.5%) were performed in diabetics. Sonographic identification of EFW over 4000 g at less than 38 weeks was associated with higher correlation between EFW and birth weight than ultrasound performed after 38 weeks (71.5 versus 259.4 g, p < .024). EFW to birth weight correlation was within 1.7% of birth weight for ultrasound performed less than 38 weeks and within 6.5% of birth weight for ultrasound performed at greater than 38 weeks.

Conclusions: Identification of EFW with ultrasound performed less than 38 weeks has greater reliability of predicting fetal macrosomia at birth than measurements performed later in gestation. EFW to birth weight correlation was more accurate than previous reports.

Keywords:

• Diabetes
• fetal ultrasound
• macrosomia
• third trimester

Acknowledgements

Data were presented at the 2016 American College of Obstetricians & Gynecologists (ACOG) Annual Scientific Meeting in Washington, DC under poster title, Fetal Macrosomia Prediction in Diabetic Gravidas: The Reliability of Third Trimester Ultrasound.

Disclosure statement

The authors declare that they have no conflict of interest. The corresponding author has full control of all primary data and can provide these data to the journal if requested.

Additional information

Funding

Statistical analysis services were funded in part with Federal funds (grant # UL1TR000101 previously UL1RR031975) from the National Center for Advancing Translational Sciences (NCATS), National Institutes of Health (NIH), through the Clinical and Translational Science Awards Program (CTSA), a trademark of DHHS, part of the Roadmap Initiative, “Re-Engineering the Clinical Research Enterprise”.