Maternal insulin-like growth factor binding protein-1, body mass index, and fetal growth

Aim-To examine the hypothesis that the maternal insulin-like growth factor system may constrain fetal growth. Methods-A prospective observational study of maternal serum insulin-like gr owth factor binding protein-1 (IGFBP-1) and fetal growth was undertaken in neonates with birthweights below the 5th centile. They had been classified either as having fetal growth restriction (FGR) due to placental dysfunctio n (increased umbilical artery Doppler pulsatility index (PI); n = 25) or as being small for gestational age (SGA; normal umbilical artery PI, growth v elocity and amniotic fluid; n = 27). Eighty nine controls had normal birthw eights (5th-95th centile), umbilical artery PI, growth velocity, and amniot ic fluid. IGFBP-1 was measured by radioimmunoassay. Results-Among the controls, there was no significant correlation between IG FBP-1 and birthweight after allowing for body mass index (BMI). Maternal BM I was high in FGR and after adjusting for this, IGFBP-1 was increased (109 ng/ml) compared with SGA babies (69 ng/ml) and controls (57 ng/ml) and corr elated with the umbilical artery PI. Conclusions-Maternal IGFBP-1 is probably not part of normal placental funct ion. Its increase in FGR could be the cause or consequence of impaired plac ental perfusion, but high IGFBP-1 concentrations might further reduce the a vailability of maternal IGF-I to the placenta. This could worsen placental function and so adversely affect fetal growth.