Fetal growth cessation in late pregnancy: its impact on predicted size parameters used to classify small for gestational age neonates

Abstract

Objective To investigate growth cessation at term and birth characteristic predictions in a large sample using Individualized Growth Assessment. Methods A prospective longitudinal study of 119 pregnancies with normal growth outcomes was carried out from 18 weeks, MA, to delivery. Measurements of head circumference (HC), abdominal circumference (AC), femur diaphysis length (FDL), mid-thigh circumference (ThC), head profile cube (Hcube), abdominal profile cube (Acube) and mid-arm circumference (ArmC) were obtained using 3D ultrasonography at 3–4 week intervals. Rossavik growth models were determined from these data using sample-specific and previously published procedures. These models were used to predict birth characteristics at different ages. Predicted and measured birth characteristics were compared and Percent Differences (% Diff) calculated. Growth cessation age [GCA] was defined by the absence of systematic change in % Diff values [derived from predictions at GCA’s] in those fetuses delivering after the GCA. Systematic (mean % Diff) and random (% Diff 95% range) prediction errors were compared to published data and when using different assumptions about growth cessation. New Growth Potential Realization Index [GPRI] reference ranges were established. Results Growth cessation ages were 38 weeks for HC, AC, THC, WT and ArmC [CHL: 38.5 weeks]. Assuming growth-to-delivery gave positive slopes [4/6 different from zero] and non-random distributions for % Differences after the 38 weeks. Systematic and random prediction errors, based on predictions at the GCA’s, were similar to those published previously except for WT [based on Hcube and Acube]. However, predicted weights derived from BPD, AC and TVol had prediction errors of −4.1+/−8.3%. After correction for non-zero systematic prediction errors [AC, ThC, ArmC, WT], mean GPRI values were close to 100, with normal ranges similar [WT larger] than those obtained previously. Conclusions Growth cessation at term occurred for all six birth characteristics studied. Prediction errors and GPRI normal ranges in this large sample were similar to those obtained previously in much smaller samples. A simple weight estimation procedure utilizing three anatomical parameters (BPD, AC, TVol) gave the most precise WT predictions. Our results provide the methods and standards required to individualize the assessment of neonatal growth outcome.

Fetal growth pathology score: a novel ultrasound parameter for individualized assessment of third trimester growth abnormalities

“…As shown in Figure 3, GPRI values were calculated using actual and predicted neonatal measurements [7]. Predicted values for WT, HC and CHL were obtained using the Rossavik size models for various anatomical parameters and a prediction age of 38 weeks (38.5 weeks for CHL), to adjust for late term growth cessation that occurs in fetuses with normal neonatal growth outcomes [7].…”

“…Predicted values for WT, HC and CHL were obtained using the Rossavik size models for various anatomical parameters and a prediction age of 38 weeks (38.5 weeks for CHL), to adjust for late term growth cessation that occurs in fetuses with normal neonatal growth outcomes [7]. The predicted WT was calculated from the set of predicted values for the parameters used in the weight estimation function while the predicted CHL was calculated using the predicted FDL value and the function relating CHL to FDL given previously [9].…”

“…This measure was used to separate neonates with normal growth outcomes from those with GR (boundary value: −0.69%). Previous studies have shown that this boundary effectively separates normally grown and growth restricted SGA neonates identified with the negative GPRI profile or placental assessment [7,9]. …”

“…These growth velocities specify Rossavik size models that provide individualized third trimester size standards and predicted birth characteristics (eliminating most between-individual variability) for up to 13 size parameters [6,7]. IGA also permits direct comparisons of fetal and neonatal growth outcome assessments on a personalized basis.…”

“…We propose the fetal growth pathology score (FGPS (Figure 2, Appendix)), which represents the cumulative moving average of %Dev p values of an individual growth parameter or sets of such parameters, for this purpose. As the first test of the usefulness of the FGPS, we compared third trimester growth categories, based on the FGPS1 (head circumference (HC), abdominal circumference (AC), femur diaphysis length (FDL), estimated weight (EWT)), to corresponding neonatal growth outcomes defined by the average, negative, pathological, GPRI (av – pGPRI: weight (WT), HC, crown-heel length (CHL), Figure 3) in a cohort of SGA pregnancies [7,9]. The latter is the pathological component of the parameter (GPRI) that is used to evaluate neonatal growth outcomes on an individualized basis [9].…”