Longitudinal Assessment of Abdominal Circumference versus Estimated Fetal Weight in the Detection of Late Fetal Growth Restriction.

OBJECTIVES: To perform a longitudinal assessment comparison between estimated fetal weight (EFW) and abdominal circumference (AC) in the prediction of late fetal growth restriction (FGR) as opposed to small for gestational age (SGA). PATIENTS AND METHODS: A cohort of unselected singleton pregnancies scanned at 32±2 and 37±1 weeks was created. Longitudinal growth assessment by calculating the conditional AC and conditional EFW was performed, and both parameters were compared for their prediction capacity for late FGR and SGA. Conditional standards set an expected size (EFW or AC) given a first measurement performed earlier. A declining growth was defined as a conditional growth of <10th centile. RESULTS: A total of 938 pregnancies were included. As expected, declining growth between 32±2 and 37±1 weeks was associated with late FGR and SGA, but the predictive capacity of both conditional AC and conditional EFW was comparably poor, with detection rates of 28% at a 10% rate of false positives for late FGR. CONCLUSIONS: Longitudinal assessment of fetal growth during the third trimester has a low predictive capacity for late FGR, with no differences between conditional AC and conditional EFW.

Third-Trimester Conditional Reference Values for Longitudinal Fetal Growth Assessment.

OBJECTIVES: The aim of this study was to derive longitudinal reference values of fetal growth (estimated fetal weight [EFW] and abdominal circumference [AC]) during the third trimester and to develop coefficients for conditional growth assessment. PATIENTS AND METHODS: A prospective cohort study was conducted involving consecutive singleton pregnancies in a low-risk population for a routine third-trimester scan at 30+0-34+6 weeks and follow-up at 37+0-38+6 weeks for an additional ultrasound. Statistical analysis was based on multilevel modeling using MLwiN software. Unconditional centiles were calculated from z-values at each gestational age, and conditional centiles were calculated from z-values at a given measurement (30-34 weeks) and the expected measurement (37-38 weeks). RESULTS: At 30-34 weeks, 8 and 9.3% of the fetuses had an unconditional EFW below the 10th and above the 90th centile, respectively. At 37-38 weeks, these figures were 10.3 and 9.3%, respectively. Regarding the unconditional AC, at the first scan, 8.9 and 9.6% had values below the 10th and above the 90th centile, while at the second scan 10.5 and 10.5% had values below the 10th and above the 90th centile, respectively. The proportion with a conditional EFW below the 10th and above the 90th centile was 10.2 and 9.4% at the second scan, respectively. For conditional AC, these figures were 10.7 and 10.3%, respectively. CONCLUSION: We have produced reference centiles for EFW and AC growth during the third trimester as a useful tool for quantifying growth.

Second- to Third-Trimester Longitudinal Growth Assessment for the Prediction of Largeness for Gestational Age and Macrosomia in an Unselected Population.

BACKGROUND: Prenatal detection of excessive growth remains inaccurate. Most strategies rely on a single cross-sectional evaluation of fetal size during the third trimester. OBJECTIVES: To compare second- to third-trimester longitudinal growth assessment with cross-sectional evaluation at the third trimester in the prediction of largeness for gestational age (LGA) and macrosomia. METHODS: A cohort of 2,696 unselected singleton pregnancies scanned at 21 ± 2 and 32 ± 2 weeks was created. Abdominal circumference (AC) measurements were transformed to z values according to the INTERGROWTH-21st standards. Longitudinal growth assessment was performed by calculation of z velocity and conditional growth. Both methods were compared to cross-sectional assessment at 32 ± 2 weeks. Predictive performance for LGA and macrosomia was determined by receiver operating characteristic curve analysis. RESULT: A total of 188 (7%) newborns qualified for LGA and 182 (6.8%) for macrosomia. The areas under the curve (AUCs) for 32-week AC z score, AC z velocity, and conditional AC were 0.78, 0.61, and 0.55, respectively, for the prediction of LGA, and 0.75, 0.61, and 0.55, respectively, for the prediction of macrosomia. Both AUCs of AC z velocity and conditional AC were significantly lower (p < 0.001) than the AUC of cross-sectional AC z scores. CONCLUSIONS: In the general population, second- to third-trimester longitudinal assessment of fetal growth is inferior to third-trimester cross-sectional evaluation of size in the prediction of LGA and macrosomia.