AMNIOTIC-FLUID GLYCINE-VALINE RATIO AND NEONATAL MORBIDITY IN FETAL GROWTH RESTRICTION

Objective: To test the hypothesis that an elevated amniotic fluid glyc ine-valine ratio predicts neonatal morbidity in growth-restricted newb orns. Methods: Amniotic fluid (AF) was collected from 122 third-trimes ter pregnancies (range 31-39 weeks), 49 of which were complicated by f etal growth restriction. Amino acid analysis was performed by high-pre ssure liquid chromatography. Glycine-valine ratios were compared betwe en normal and growth-restricted fetuses. Neonatal morbidity within the group of growth-restricted fetuses was characterized by evaluation of neonatal hypoglycemia, arterial cord blood gas analysis, and birth we ight percentile. We also examined the correlation of AF glycine-valine ratio to the umbilical artery resistance index. The median interval b etween AF sampling and delivery was 1 day (range 0-8 days). Analyses w ere performed by Student t test, X-2 with Yates correction, or simple correlation when appropriate. P < .05 was considered significant. Resu lts: Growth-restricted fetuses have a significantly elevated AF glycin e-valine ratio compared with control subjects (3.31 +/- 1.06 versus 2. 61 +/- 0.77, respectively, P < .001). There was no association of the glycine-valine ratio with gestational age for either group. An elevate d glycine-valine ratio was not associated with neonatal hypoglycemia w ithin the growth-restricted group (hypoglycemia: [n = 16] 3.19 +/- 1.0 7; no hypoglycemia: (n = 30) 3.44 +/- 1.09). There were no significant correlations of glycine-valine ratio with arterial cord blood pH (r = -0.10), oxygen pressure (r = 0.04), or base deficit (r = 0.12). There were no significant correlations of glycine-valine ratio and birth we ight percentile (r = -.24) or umbilical artery resistance index (r = - .14). Conclusion: Amniotic fluid glycine-valine ratio is elevated in g rowth-restricted fetuses compared with control fetuses. However, the l evel of glycine-valine elevation is not associated with neonatal morbi dity related to hypoglycemia, arterial cord blood gas abnormalities, o r birth weight percentile. (C) 1997 by The American College of Obstetr icians and Gynecologists.