Umbilical cord serum insulin-like growth factor-1 is associated with growth of fetal fractional limb volume: A prospective study.

Introduction: Insulin-like growth factor-1 (IGF-1) promotes protein and carbohydrate metabolism, which consequently affects birth weight. Fetal fractional limb volume has been proposed as a useful parameter for predicting birth weight and quantifying fetal soft tissue development. However, the relationship between umbilical cord serum IGF-1 levels and fetal fractional limb volume remains unclear. Herein, we aimed to investigate the association of cord serum IGF-1 levels with longitudinal changes in fetal fractional limb volume in uncomplicated pregnancies.

Material and methods: In this prospective study, 96 singleton pregnancies were followed. Fetal 3D ultrasonography was performed longitudinally at 24, 30, and 36 weeks of gestation to assess fractional arm volume and thigh volumes as cylindrical limb volumes, derived from 50% of the fetal total diaphysis length. Cord serum IGF-1 levels were measured using an electrochemiluminescence immunoassay. The relationship between cord blood IGF-1 levels and fetal fractional limb volume was analyzed using multiple linear regression; adjusted for potential confounding factors including maternal age, parity, pre-pregnancy body mass index, gestational weight gain, fetal sex, and gestational age at assessments.

Results: Mean cord serum IGF-1 was 52.8 ± 18.4 ng/mL (mean ± SD). IGF-1 levels were not associated with fetal fractional limb volumes at 24 weeks and 30 weeks but were significantly correlated with fractional arm volume (r = 0.290, p = 0.006) and fractional thigh volume (r = 0.289, p = 0.006) at 36 weeks. After adjusting for covariates, cord serum IGF-1 explained 7.0% and 10.6% of the variation in fractional arm and thigh volumes at 36 weeks, respectively. Although IGF-1 was significantly correlated with the birth weight percentile, it did not correlate with the estimated fetal weight at 36 weeks.

Conclusions: Cord serum IGF-1 levels significantly correlated with fetal fractional limb volumes in late gestation. Fractional limb volume may be an earlier and more sensitive ultrasound parameter affected by serum IGF-1 level than estimated fetal weight.