Factors affecting cord blood leptin levels in a consecutive birth cohort

Introduction: The fetus that fails to meet its ideal growth trajectory has increased risks of poor health outcomes throughout life. "Gold standard" methods of anthropometric assessment such as measurement of percentage body fat can be difficult to apply across populations and other biomarkers such as serum concentration of umbilical cord blood leptin may be more effective for screening. This study reports cord blood leptin levels in a large prospective consecutive birth cohort and assesses the relationship between leptin and neonatal and maternal factors.

Methods: Venous umbilical cord blood samples were collected from a prospective consecutive cohort of pregnancies at the time of delivery. Maternal and neonatal characteristics and details of delivery were collated. Serum leptin levels were measured, associations with demographic features were identified, and a normal range was established. The association between cord leptin level and neonatal outcome was tested.

Results: Umbilical cord leptin and maternal and neonatal characteristics were collected at 1275 births. The median leptin value was 10.8 ng/ml (IQR: 6.4, 17.8 ng/ml). Log₁₀ leptin was significantly associated with gestation at delivery, birthweight (BWt), infant sex, plurality, and maternal body mass index (BMI) (p < .001). Observed leptin values were expressed as multiples of the median (MoM). The mean leptin MoM was significantly lower in infants admitted to NICU following delivery (0.85; 95% confidence interval [CI]: 0.78-0.91 versus 1.05; 95% CI: 1.03-1.06 (controls), p < .001). There was no significant association between leptin MoM values and 5-min Apgar scores.

Conclusions: Neonatal cord leptin levels are influenced by a number of maternal and fetal characteristics. Absolute levels can be adjusted to account for normal population variation. Infants requiring admission to NICU have lower mean leptin MoM levels. Further studies are needed to see whether the identification of fetuses with polarized leptin levels (<5th or >95th centile) will benefit from further surveillance or intervention in infancy.