Nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 levels in human amniotic fluid

Neurotrophins are proteins that promote neuronal growth and differentiation. In this pilot study we determined whether the neurotrophins nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 were present in amniotic fluid specimens to begin to elucidate their developmental regulation. We also explored associations between neurotrophin levels and central nervous system abnormalities and exposure to infection.

One hundred thirty-four amniotic fluid specimens were obtained from women undergoing amniocentesis at University of North Carolina Hospitals. Each specimen was assayed by enzyme-linked immunosorbent assay for nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3. Associations of maternal age, gestational age, and maternal ethnicity with neurotrophin levels were explored. Neurotrophin levels in pregnancies in which there was enlargement of the fetal cerebral lateral ventricles or exposure to infection were compared with those in control pregnancies. Spearman correlational analyses and analyses of covariance were performed, with adjustment for gestational age.

Nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3 were detected in all amniotic fluid specimens. Nerve growth factor increased with gestational age (P =.045). Brain-derived neurotrophic factor decreased with gestational age (P =.035). Patients with ventriculomegaly (with or without other central nervous system abnormalities) on ultrasonographic examination (n = 6) had significantly lower nerve growth factor levels than control subjects (P =.0046); patients with evidence of infection (n = 5) during pregnancy had significantly lower nerve growth factor (P =.0037) and brain-derived neurotrophic factor (P =.0362) levels.

Nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3 are detectable in amniotic fluid and vary with gestational age. Decreased nerve growth factor and brain-derived neurotrophic factor levels in amniotic fluid may be a marker for the presence of central nervous system abnormalities, infectious insults in utero, or both.