Prenatal prediction of neonatal growth status in twins using individualized growth assessment.

OBJECTIVE: To determine if the growth status at birth of twins can be predicted in the third trimester using the Prenatal Growth Assessment Score (PGAS). METHODS: The growth of 40 twin fetuses were studied with ultrasound from 14 weeks until delivery. Measurements of the head circumference (HC), abdominal circumference (AC), thigh circumference (ThC), femur diaphysis length (FDL), head cube (A), and abdominal cube (B) were made at 2 to 3 week intervals. Rossavik growth models for these parameters were determined from second trimester measurements. These models were used to define expected third trimester growth curves and birth characteristics. Comparisons of expected and actual third trimester measurements were used to calculate PGAS values after various time points (PGASAt) and after the last time point (PGASAT). Similar comparisons after birth were used to determine Growth Potential Realization Index (GPRI) values for HC, AC, ThC, weight (WT), and crown-heel length (CHL), with and without correction for decreased soft tissue deposition. These two sets of GPRI values were used to calculate two sets of Neonatal Growth Assessment Scores (NGASS, NGASTw). Using NGASS and NGASTw (as well as GPRI values in some cases), the twin neonates were classified as Normal (N), Decreased Soft Tissue Deposition, (DSTD), Intrauterine Growth Retardation (IUGR) and Macrosomia (M). RESULTS: At birth 22/40 (55%) were classified as N, 9/40 (22.5%) as DSTD, 6/40 (15.0%) as IUGR, and 3/40 (7.5%) as M. All -PGASAT values in the N group were greater than -0.40% with one exception (-PGASAT = -0.43%). All PGASAt values were above this same boundary except for one fetus. No differences were seen between the N and DSTD groups [mean -PGASAT (range): N, -0.12% (0% to -0.34%); DSTD, -0.10% (0% to -0.30%)]. The IUGR group had 4 fetuses with -PGASAT values between -0.65% and 2.79% and two with values of 0.0% and -0.12%. Growth retardation in the latter two was limited to a decrease in thigh soft tissue deposition. -PGASAt values in the first 4 fetuses were below -0.40% 1.6 to 9.5 weeks before delivery (mean: 6.1 weeks). Fetuses in group M had +PGASAT values of 0.0%, +1.8%, and +1.2%. PGASAt values were above +0.40% at 3.6 and 9.8 weeks before delivery in the latter two fetuses. CONCLUSIONS: These results support the concept that PGASAT and PGASAt values outside +/- 0.40% indicate either IUGR or macrosomia. Almost all fetuses with growth problems in the third trimester can be detected, on average, 6 weeks before delivery unless the growth abnormality is limited to decreased soft tissue deposition.

Modified neonatal growth assessment score: a multivariate approach to the detection of intrauterine growth retardation in the neonate.

The objective of this investigation was the development of a modified Neonatal Growth Assessment Score (mNGAS) for use in the evaluation of neonatal growth status. The growth of 74 fetuses at risk for intrauterine growth retardation (IUGR) was followed longitudinally, beginning in the first or early second trimester. Rossavik growth models derived from data obtained in the second trimester were used to predict the weight (WT), crown-heel length (CHL) and head (HC), abdominal (AC) and thigh circumferences (ThC) at birth, which were then actually measured within 24 h after delivery. These measurements were compared to age-specific size curves and used to calculate sets of five growth potential index (GPRIi) values, which in turn were used to calculate five-variable Neonatal Growth Assessment Scores (NGAS5). Neonates were initially classified as normal or IUGR on the basis of NGAS5, GPRIi, and anatomic measurements. A final classification based on principal component analysis and linear discriminant analysis was carried out. The score obtained using the first principal component function was defined to be mNGAS51. The effectiveness of mNGASij values, determined from 1-4 GPRIi values, in separating normal and IUGR neonates was also evaluated. Neonates initially considered to be normal had very few abnormal GPRI values or anatomic measurements, whereas the frequency of these abnormalities in IUGR neonates was significantly increased. However, no single anatomic variable was 100% normal in the normal neonates and 100% abnormal in IUGR neonates. Only 40% of IUGR neonates were small for gestational age. Classification of these neonates using principal component analysis and linear discriminant analysis was essentially the same (98.6%) as that made initially after reclassification of two IUGR neonates as normal. The characteristics of the initial and final normal and IUGR groups were very similar and the mNGAS51 was strongly correlated with the NGAS5 in the IUGR group. The effectiveness of mNGASij in separating normal and IUGR neonates increased with the number of GPRIi values included and the types used. GPRIThC and GPRIWT were the most important, followed by GPRIAC. GPRICHL and GPRIHC were much less important and in some cases detrimental. These findings support the concepts of a decrease in soft tissue mass as the initial step in the development of IUGR and the protection of head growth (brain-sparing). The characteristics of mNGAS51, particularly its comprehensiveness, its independence of differences in growth potential, its weighting of GPRIi values according to their importance in the detection of IUGR and its ability to detect different manifestations of IUGR in different individuals, indicate that this should be a most effective parameter for separating normal and IUGR neonates.

Evaluation of twin growth status at birth using individualized growth assessment: comparison with conventional methods.

OBJECTIVE: We sought to evaluate the growth status of twins at birth using individualized growth assessment methods and to compare this assessment with that obtained with conventional methods. STUDY DESIGN: Twenty twin pregnancies were studied longitudinally with ultrasound. Measurements of the head and abdominal cubes (A,B), head circumference (HC), abdominal circumference (AC), thigh circumference (ThC), and femur diaphysis length (FDL) made in the 2nd trimester were used to specify Rossavik growth models for each parameter in each fetus. These models were used to predict weight (WT), HC, AC, ThC, and crown-head length (CHL) at birth. Actual birth measurements made within 24 hours of delivery were compared to predicted values, the latter corrected using singleton [corrects for both technical problems (TP)] or twin [corrects for both technical problems (TP) and decreased soft-tissue deposition (DSTD)] correction factors where appropriate. Two sets of growth potential realization index (GPRI) values and their corresponding neonatal growth assessment scores (NGAS) were calculated and compared to previously established normal values. Birth measurements were compared with appropriate population age-specific size curves. These data were used to characterize and classify the growth status of each twin neonate. RESULTS: Individualized growth assessment identified five primary types of growth outcomes: normal (Group I, 45%); primarily DSTD (Group II, 22.5%); IUGR (Group III, 15%); above average soft-tissue deposition (Group IV, 5%); and growth acceleration (Group V, 7.5%). Within Group I was a subgroup with evidence of DSTD (Group Ib, 33.3% of Group I). Group II could be divided into two subgroups, one with only DSTD (Group IIa, 44.4% of Group II) and one with both DSTD and other growth abnormalities (Group IIb, 55.6% of Group II). Group III had multiple growth abnormalities which were more severe than those seen in Group II. All normal neonates were AGA and had virtually all anatomic parameters within their respective normal ranges. Of the neonates with definite evidence of IUGR (Groups IIb and III), only 4 of 11 (36.4%) were SGA and only 6 of 11 (54.5%) had any of the five anatomic parameters below their respective normal ranges. Only 1 of 3 (33.3%) of neonates with growth acceleration was LGA and none (0%) of the five anatomic parameters were above their respective normal ranges. CONCLUSIONS: Individualized growth assessment methods provide a more comprehensive assessment of growth outcome in twins and detect a decrease in soft-tissue deposition not identifiable with conventional growth assessment procedures. The latter procedures are also less sensitive in the detection of both IUGR and growth acceleration.

Prediction of neonatal crown-heel length in normal singletons, twins, and triplets using individualized growth assessment.

In groups of normally growing singletons (20), twins (20), and triplets (13), predicted femur diaphysis length (FDL) values at birth were obtained using Rossavik growth models specified from second-trimester ultrasound studies of fetal growth. Six previously published functions were utilized to obtain predicted crown-heel length (CHL) values from predicted FDL values. These values were compared to the actual CHL values and the percent differences calculated. Based on their systematic (mean percent difference) and random (standard deviation of percent difference) prediction errors, the functions of Vintzileos (singletons), Hadlock (twins), and Brown (triplets) were found to give optimal results (no systematic error; random error: +/- 6%). Using predicted CHL values obtained with these optimal functions, growth potential realization index values for CHL (GPRICHL) were determined for singletons, twins, and triplets. In all three groups, the mean GPRICHL value was 100% with a range of approximately 95% to 105%. These results indicate that the CHL can be predicted from second-trimester growth patterns and evaluated using individualized growth assessment methods.