Insulin-like growth factors (IGF) 1 and 2 in human foetal plasma and relationship to gestational age and foetal size during midpregnancy

Abstract

Abstract. 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.