S100B Protein Concentrations in Amniotic Fluid Correlate with Gestational Age and with Cerebral Ultrasound Scanning Results in Healthy Fetuses

Abstract

S100B is an acidic calcium-binding protein of the EF-hand family present in the central nervous system, where it is concentrated mainly in glial cells (1). It has been suggested that this protein is involved in various cellular functions (e.g., cell-cell communication, cell growth, cell structure, energy metabolism, and intracellular signal transduction) and that it may also act as a cytokine with neurotrophic effects at physiological concentrations. In this regard, studies in experimental models on laboratory animals and cell cultures have shown that decreased S100B expression in the nervous tissue correlates with neurobehavioral abnormalities and with microcephaly as a result of in utero cocaine exposure (2)(3). In humans, umbilical blood cord concentrations of S100B have been shown to be inversely correlated with gestational age, suggesting a neurotrophic role for this protein in the third trimester of pregnancy (4). On the other hand, its appearance at high concentrations in biological fluids has been shown to be a reliable marker of brain lesion in adults and pediatric patients and, recently, in the perinatal period (5)(6)(7)(8). In particular, the appearance of S100B protein in the amniotic fluid of anencephalic fetuses is considered an indicator of damage in the central nervous system associated with neural tube defects (9). This study provides reference values of S100B amniotic fluid concentrations during the second trimester of pregnancy. We investigated, between the 15th and 18th weeks of gestation (mean, 16.5 weeks), 322 women (mean age, 35.5 ± 2.7 years; 35 years, n = 199) with consecutive physiological singleton pregnancies, who underwent amniocentesis for chromosomal abnormality exclusion (from June 1995 to November 1997). Appropriate fetal growth was defined by the presence of ultrasonographic signs (when the biparietal diameter and abdominal circumference were …