ac in pregnancy normal range?

EP14.11: The normal range of fetal abdominal circumference velocity between 20 and 36 weeks of gestation
To create a reference chart for abdominal circumference (AC) growth velocity between 20 and 36 weeks gestation in singleton pregnancies.
Methods

Observational longitudinal study of all women attending for pregnancy care at the John Radcliffe Hospital, Oxford, UK between May 2016 and February 2017. All women have routine scans at 20 and 36 weeks gestation. Fetuses with AC measurements performed between 19+0 and 21+6 weeks and then again between 35+0 and 36+6 were included. Exclusion criteria were multiple pregnancy, abnormal karyotype, major fetal abnormalities and absent data on first-trimester dating. The quality of AC images and reliability of measurements were assessed according to INTERGROWTH-21st criteria. Local regression models were fitted separately at the 20 and 36 week gestational windows, in order to estimate the AC mean and standard deviation (SD), and Z scores were calculated. AC growth velocity was defined as the Z score difference between 20 and 36 weeks divided by the interval in days between the two ultrasound evaluations and multiplied by 100.
Results

The study population included 3334 fetuses. Given the narrow gestational age windows, a linear model provided the best fit for median AC and SD. The equations at 20 weeks were: mean AC=-68.349+1.571*GA and SD=1.253*(-2.038+0.050*GA). The equations at 36 weeks were: mean AC=53.090+1.081*GA and SD=1.253*(0.497+0.046*GA). Mean AC growth velocity between 20 and 36 weeks was -0.0018 (±1.041). The 3rd, 5th, 10th, 50th, 90th, 95th and 97th centiles of AC growth velocity were -1.8997, -1.6785, -1.3091, -0.0069, 1.3255, 1.7279, 1.9973, respectively.
Conclusions

We have defined AC growth velocity between 20 and 36 weeks and we have established its normal distribution. This provides reference values for longitudinal assessment of fetal growth. Further studies are needed in order to evaluate the clinical significance of growth patterns in the tail ends of this normal distribution.

Volume50, IssueS1

Special Issue: Abstracts of the 27th World Congress on Ultrasound in Obstetrics and Gynecology, 16–19 September 2017, Vienna, Austria

September 2017

Pages 317-318

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