Standardization of amniotic fluid leptin levels and utility in maternal overweight and fetal undergrowth.

OBJECTIVE

Leptin is an adipokine that regulates energy homeostasis. The objective of this study was to establish a gestational age-specific standard for amniotic fluid leptin (AFL) levels and examine the relationship between AFL, maternal overweight and fetal growth restriction.

STUDY

DESIGN

Amniotic fluid was obtained at mid-gestation from singleton gravidas, and leptin was quantified using enzyme-linked immunosorbent assay. Amniotic fluid samples from 321 term pregnancies were analyzed. Clinical data, including fetal ultrasound measurements and maternal and infant characteristics, were available for a subset of patients (n=45).

RESULTS

The median interquartile range AFL level was significantly higher at 14 weeks' gestation (2133 pg ml(-1) (1703 to 4347)) than after 33 weeks' gestation (519 pg ml(-1) (380 to 761), P trend<0.0001), an average difference of 102 pg ml(-1) per week. AFL levels were positively correlated with maternal pre-pregnancy body mass index (BMI) (r=0.36, P=0.03) adjusting for gestational age at measurement, but were not associated with fetal growth.

CONCLUSIONS

AFL levels are higher at mid-gestation than at late gestation, and are associated with maternal pre-pregnancy BMI.