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 growth 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 dysfunction (increased umbilical artery Doppler pulsatility index (PI); n = 25) or as being small for gestational age (SGA; normal umbilical artery PI, growth velocity and amniotic fluid; n = 27). Eighty nine controls had normal birthweights (5th–95th centile), umbilical artery PI, growth velocity, and amniotic fluid. IGFBP-1 was measured by radioimmunoassay.
RESULTS Among the controls, there was no significant correlation between IGFBP-1 and birthweight after allowing for body mass index (BMI). Maternal BMI 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 correlated with the umbilical artery PI.
CONCLUSIONS Maternal IGFBP-1 is probably not part of normal placental function. Its increase in FGR could be the cause or consequence of impaired placental perfusion, but high IGFBP-1 concentrations might further reduce the availability of maternal IGF-I to the placenta. This could worsen placental function and so adversely affect fetal growth.
Maternal insulin-like growth factor-1 (IGFBP-1) does not correlate with birthweight in normal pregnancy but concentrations are increased in fetal growth restriction (FGR)
Maternal body mass index is an important confounder when assessing the relation between maternal IGFBP-1 and fetal growth
Increased maternal IGFBP-1 in FGR may further reduce availability to the placenta of already low concentrations of IGFBP-1
Normal maternal IGFBP-1 concentrations in small for gestational age pregnancies indicates the use of umbilical artery Doppler to assess placental function when fetal size is <5th centile for gestational age
- insulin-like growth factor binding protein-1
- growth restriction
- umbilical artery
- Doppler pulsatility index
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