INSULIN-LIKE-GROWTH-FACTOR-1 IN CONTROLS AND GROWTH-RETARDED FETUSES

Objectives: To establish a reference range of insulinlike growth facto r 1 (IGF-1) values in normal fetuses and to assess whether intrauterin e growth retardation is associated with increased or decreased IGF-1 l evels. Methods: Retrospective analysis of blood samples collected from 64 fetuses who underwent blood sampling at 18-38 weeks' gestation was performed: 40 fetuses, who were considered controls, were appropriate ly grown for gestational age and were found unaffected by the conditio n for which they were tested; the remainder (n = 24) underwent fetal b lood sampling to assess fetal karyotype and acid-base balance followin g ultrasonic diagnosis of intrauterine growth retardation. (In this gr oup, 8 survived, and 16 died during the perinatal period). IGF-1 was m easured using a radioimmunoassay after acid-ethanol extraction in orde r to avoid interference by the binding proteins. All samples from cont rols and growth-retarded fetuses were measured using the same batch, a nd the intraassay coefficient of variation of the test ranged from 4.1 to 6.1%. Results: In control fetuses, IGF-1 serum levels increased li nearly with gestational age. In growth-retarded fetuses, IGF-I levels were not significantly different from the reference range (median Z-sc ore -0.3; range -4.4 to 291)and did not correlate with fetal size, hem atocrit, and acid-base balance values. There was a significant differe nce in IGF-1 and pH values when the fetuses were divided into two grou ps based on the perinatal outcome: those who survived had values of IG F-1 mostly within the normal range, whereas the fetuses who died in ut ero or postnatally had significantly decreased pH and elevated IGF-1 v alues (median Z-score 2.1; 95% confidence interval 0.4-13.9; p = 0.04) , Conclusions: This study confirms previous observations that IGF-1 le vels parallel the increase in fetal size which occurs with advancing g estation. Increased levels of IGF-1 may indicate a terminal process in the fetal adaptation to placental failure.