INSULIN-LIKE GROWTH-FACTORS (IGF)-1 AND (IGF)-2 IN HUMAN-FETAL PLASMA AND RELATIONSHIP TO GESTATIONAL-AGE AND FETAL SIZE DURING MIDPREGNANCY

IGF-1 and IGF-2 were measured by specific radioimmunoassay after acid-ethanol extraction of plasma obtained by foetoscopy from 20 normal foetuses aged 15-23 weeks. IGF-1 and IGF-2 levels were 36 .+-. 11 and 162 .+-. 55 ng/ml, respectively. In comparison, levels in cord blood were 84 .+-. 58 and 264 .+-. 176 ng/ml, respectively, and in adult plasma were 410 .+-. 106 and 818 .+-. 272 ng/ml. Both IGF-1 and IGF-2 were in the normal foetal range in a further three foetuses with anencephaly and two foetuses with spina bifida. No sex difference was observed. IGF-1 was positively correlated with foetal body weight (P < 0.001), placenta weight (P < 0.02) and with body length measured crown-rump (P < 0.01) or crown-heel (P < 0.02). No correlation between IGF-2 and body weight, length, placenta weight or gestational age was found. Both IGF-1 and IGF-2 are present in the human foetal circulation earlier in gestation than has previously been demonstrated, the levels being low throughout this period of gestation in comparison with adult plasma.