Characterization of the insulin-like growth factor axis in term pregnancies complicated by maternal obesity.

STUDY QUESTION: Does maternal obesity affect insulin-like growth factor (IGF) axis protein expression patterns in maternal and cord blood?

SUMMARY ANSWER: Maternal obesity attenuates cord blood expression of IGF-binding protein (IGFBP)-4.

WHAT IS KNOWN AND WHAT THIS PAPER ADDS: The IGF axis plays a critical role in fetal growth and development. Maternal obesity compromises IGF axis protein expression in fetal circulation, which is consistent with the findings of epidemiological studies suggesting that maternal obesity has an independent effect on fetal growth signals during in utero development.

STUDY DESIGN: This cross-sectional case-control study involved 12 lean [body mass index (BMI) 18.5-24.9 kg/m2] and 12 obese (BMI≥30 kg/m2) women and their neonates at term. At the completion of the study, IGF axis protein expression and hormone concentrations in both maternal and cord blood were examined.

PARTICIPANTS AND SETTING: We obtained fasting serum samples from cases and controls matched for age, gestation, mode of delivery, parity and glucose tolerance prior to and immediately following elective caesarean section. The corresponding umbilical cord blood was also collected at birth.

MAIN RESULTS AND THE ROLE OF CHANCE: Between-group comparisons revealed elevated maternal insulin (P=0.03) and leptin (P<0.01) concentrations in obese gravidas. After adjustment, the maternal homeostasis model of assessment-insulin resistance (HOMA-IR) score was positively correlated with both maternal BMI and leptin levels (P<0.01). Umbilical cord blood levels of IGFBP-3 showed an inverse trend to maternal HOMA-IR (P=0.03) but were directly related to the fetal-placental weight ratio (P<0.01). In cord serum from obese mothers, IGFBP-4 expression was attenuated compared with the controls (P<0.05).

LIMITATIONS: The limitations of our study include the cross-sectional design and relatively small sample size.

WIDER IMPLICATIONS: Our results provide preliminary evidence for the applicability of our findings to other ethnic groups when pregnancy is complicated by obesity.

STUDY FUNDING/COMPETING INTERESTS: This work was supported by the University of Ottawa, Faculty of Health Sciences/Children's Hospital of Eastern Ontario Research Partnership Grant awarded to K.B.A. and Z.M.F. The authors have no conflicts of interest to declare.