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 cir cumference (HC), abdominal circumference (AC), thigh circumference (Th C), 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 trimes ter measurements were used to calculate PGAS values after various time points (PGAS(At)) and after the last time point (PGAS(AT)). Similar c omparisons after birth were used to determine Growth Potential Realiza tion Index (GPRI) values for HC, AC, ThC, weight (WT), and crown-heel length (CHL), with and without correction for decreased soft tissue de position. These two sets of GPRI values were used to calculate two set s of Neonatal Growth Assessment Scores (NGAS(S), NGAS(Tw)). Using NGAS (S) and NGAS(Tw) (as well as GPRI values in some cases), the twin neon ates were classified as Normal (N), Decreased Soft Tissue Deposition, (DSTD), Intrauterine Growth Retardation (IUGR), and Macrosomia (M). Re sults: 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 -PGAS(AT) values in the N group were greater than -0.40% with one exception (-PGAS(AT) = - 0.43%). All PGAS(At) values were above this same boundary except for o ne fetus. No differences were seen between the N and DSTD groups [mean -PGAS(AT) (range): N, -0.12% (0% to -0.34%); DSTD, -0.10% (0% to -0.3 0%)]. The IUGR group had 4 fetuses with -PGAS(AT) 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 depo sition. -PGAS(At) 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 +PGAS(AT) values of 0.0%, +1.8%, and +1.2%. PGAS(At) values were abov e +0.40% at 3.6 and 9.8 weeks before delivery in the latter two fetuse s. Conclusions: These results support the concept that PGAS(AT) and PG AS(At) values outside +/-0.40% indicate either IUGR or macrosomia. Alm ost all fetuses with growth problems in the third trimester can be det ected, on average, 6 weeks before delivery unless the growth abnormali ty is limited to decreased soft tissue deposition. (C) 1996 John Wiley & Sons, Inc.