Calculation of gestational age in late second and third trimesters by ex vivo magnetic resonance spectroscopy of amniotic fluid

Calculation of gestational age in late second and third trimesters by ex vivo magnetic resonance spectroscopy of amniotic fluid

Presented at the 29th Annual Meeting of the Society for Maternal-Fetal Medicine, San Diego, CA, Jan. 26-31, 2009.
Brad R. Cohn, MDab, Emily Y. Fukuchi, MD, MPHf, Bonnie N. Joe, MD, PhDa, Mark G. Swanson, PhDa, John Kurhanewicz, PhDa, Jingwei Yu, PhD, MDd, Aaron B. Caughey, MD, PhD, MPHce
Received 4 June 2009; received in revised form 29 October 2009; accepted 19 January 2010. published online 03 May 2010.
Corrected Proof

Objective

The purpose of this study was to develop a reliable model for the calculation of gestational age (GA) in second and third trimesters with the use of amniotic fluid (AF) metabolite profiles that were determined by magnetic resonance spectroscopy.

Study design

High-resolution (11.7 T) ex vivo magnetic resonance spectroscopy was performed on 95 AF samples (mean, 31.7 weeks; range, 15.6–39.9 weeks). GA was determined by last menstrual period or first-trimester ultrasound scanning. Concentrations of 21 AF metabolites were measured with automated techniques. Metabolite concentrations, inverses, natural logs, and squares were entered as predictive variables in a stepwise linear regression model.

Results

The following formula was derived: GA = 64.922 – (14.456 × alanine) + (4.965 × natural log [creatinine]) – (0.931 × glucose) – (5.202 × valine). This model fit the data with an R2 value of 0.926. Average error among all samples was ±1.75 weeks (SD, ±1.43 weeks), for the second trimester was ±2.21 weeks (SD, ±1.78 weeks), and for the third trimester was ±1.59 weeks (SD, ±1.26 weeks).

Conclusion

Statistical modeling accurately predicted GA with amniotic fluid metabolite profiles that were obtained by magnetic resonance spectroscopy, which may represent a significant improvement over conventional ultrasound dating in the third trimester. Future studies should compare these techniques directly.

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http://www.ajog.org/article/S0002-9378(10)00076-1/abstract