A modified prenatal growth assessment score for the evaluation of fetal growth in the third trimester using single and composite biometric parameters

Figures & data

Figure 1. Definition of pathological Percent Deviations. Positive and negative parts of the age-specific reference range for a given anatomical parameter were subtracted from the Percent Deviation value to give the +% Dev_p and −% Dev_p values.

Table 1. Definitions of Modified Prenatal Growth Assessment Scores.

PGAS Parameter	Abbreviation	Definition
Individual anatomical parameter	iapPGAS	Pathological Percent Deviation [% Devp] for a given anatomical parameter at a specified third trimester time point (can be positive or negative)
Anatomical parameter	apPGAS	Mean value of the % Devp values obtained during the third trimester for a specific anatomical parameter (can be positive or negative)
Individual composite	icPGAS	Mean value of the % Devp values obtained at a specified third trimester time point for a set of anatomical parameters (can be positive or negative)
Composite groups	cPGAS	Mean value of the % Devp values obtained during the third trimester for a specified set of anatomical parameters (can be positive or negative) c1aPGAS HC, AC, ThC. FDL, EWTa (Hcube, Acube) c1bPGAS HC, AC, ThC. FDL, EWTb (BPD, AC, TVol) c2PGAS ArmC, AVol, ThC and TVol c3PGAS HC, AC, FDL, EWTa (Hcube, Acube)

BPD = biparietal diameter, HC = head circumference, AC = abdominal circumference, FDL = femur diaphysis length; ThC = mid-thigh circumference; TVol = fractional thigh volume; EWT = estimated weight; Hcube = (head short axis × head long axis)^1.5; Acube = (abdominal short axis × abdominal long axis)^1.5; +% Dev_p and −% Dev_p : component of % Deviation outside upper and lower limits of age-specific % Deviation reference range, respectively.

Table 2. Anatomical Parameter Prenatal Growth Assessment Scores (apPGAS).

		95% Range			Percent excluded
Parameter	N	+apPGAS	−apPGAS	No. Scans	+iapPGAS	−iapPGAS
		%	%		%	%
BPD	117	0.0 to +0.38	0.0 to −0.00	400	2.8	1.0
HC	117	0.0 to +0.00	0.0 to −0.11	400	1.1	2.5
AC	118	0.0 to +0.02	0.0 to −0.05	403	2.0	2.5
FDL	117	0.0 to +0.27	0.0 to −0.00	401	3.7	1.0
ThC	113	0.0 to +0.49	0.0 to −0.04	388	2.3	1.8
HDL	118	0.0 to +0.08	0.0 to −0.00	402	2.2	1.7
ArmC	118	0.0 to +0.17	0.0 to −0.58	402	2.5	3.0
AVol	118	0.0 to +2.30	0.0 to −0.80	402	3.7	1.7
TVol	118	0.0 to +1.76	0.0 to −0.00	403	3.5	1.2
EWT	117	0.0 to +0.06	0.0 to −0.13	399	2.0	2.3

BPD = biparietal diameter, HC = head circumference, AC = abdominal circumference, FDL = femur diaphysis length; ThC = mid-thigh circumference; TVol = fractional thigh volume; EWT = estimated weight; N = number of subjects scanned; −apPGAS and +apPGAS refers to mean values of % Dev_p values for a specific anatomical parameter (positive or negative); +iapPGAS and −iapPGAS refer to pathological Percent Deviation [% Dev_p] for a given anatomical parameter at a specified third trimester time point [positive or negative]; 95% reference ranges were determined by sorting. Percent excluded: proportion of iapPGAS values excluded from the reference range using apPGAS reference range values.

Table 3. Composite Prenatal Growth Assessment Scores (cPGAS).

		95% Range			Percent excluded
Parameter	N	+cPGAS	−cPGAS	No. Scans	+icPGAS	−icPGAS
		%	%		%	%
c1a	112	0.0 to +0.39	0.0 to −0.18	–	–	–
c1b	112	0.0 to +0.36	0.0 to −0.17	385	5.0	3.1
c2	113	0.0 to +0.89	0.0 to −0.43	387	6.7	4.4
c3	112	0.0 to +0.45	0.0 to −0.19	--	–	–

BPD = biparietal diameter, HC = head circumference, AC = abdominal circumference, FDL = femur diaphysis length; ThC = mid-thigh circumference; TVol = fractional thigh volume; EWT = estimated weight; N = number of subjects scanned; c1a = HC, AC, ThC. FDL, EWT_a (Hcube, Acube); c1b = HC, AC, ThC. FDL, EWT_b (BPD, AC, TVol); c2 = ArmC, AVol, ThC and TVol; c3 = HC, AC, FDL, EWT (Hcube, Acube); Hcube = (head short axis × head long axis )^1.5; Acube = (abdominal short axis × abdominal long axis)^1.5; 95% reference ranges were determined by sorting.

Figure 2. Evaluation of individual composite PGAS values for ic1bPGAS and ic2PGAS. These specific examples demonstrate composite parameters that include at least one soft tissue component such as fractional arm volume (AVol), fractional thigh volume (TVol), mid-arm circumference (ArmC), and mid-thigh circumference (ThC).

Table 4. Fetal growth evaluation using mPGAS.

MA	−ihcPGAS§	−iacPGAS	−ifdlPGAS	−ithcPGAS	−iewtPGAS		−ic1aPGAS†
weeks	%	%	%	%	%		%
Fetus 1: Normal growth in the third trimester
28.3	0.00	0.00	0.00	0.00	0.00		0.00
32.3	0.00	0.00	0.00	0.00	0.00		0.00
35.3	0.00	0.00	0.00	0.00	0.00		0.00
38.1	0.00	0.00	0.00	0.00	0.00		0.00
−apPGAS‡	0.00	0.00	0.00	0.00	0.00	−c1aPGAS¶	0.00
Fetus 2: IUGR in the third trimester
27.7	0.00	0.00	0.00	0.00	0.00		0.00
30.7	−1.40*	−4.76*	0.00	−0.63*	−1.30*		−1.62*
32.7	0.00	0.00	0.00	−5.27*	0.00		−1.05*
−apPGAS	−0.47*	−1.59*	0.00	−1.97*	−0.33*	−c1aPGAS	−0.87*

*Abnormal values.

†–ic1aPGAS: average of the five −iapPGAS values at specific time points

‡–apPGAS: average of all −iapPGAS values for specified anatomical parameter.

¶–c1aPGAS: average of the five −apPGAS values.

§–iapPGAS: negative individual Prenatal Growth Assessment Score for different anatomical parameters (ap).