Fetal blood cell membrane fluidity in small for gestational age fetuses.

Blood cells membrane fluidity was assessed prenatally by fluorescence polarization for anisotropy, microviscosity, degree of order and fusion activation energy in 20 fetuses who underwent percutaneous umbilical blood sampling for intrauterine growth retardation (IUGR) and in 25 controls for normal weight sampled for other indications. Simultaneously, blood samples were collected from each mother for comparison. Regulators of membrane fluidity (i.e., cholesterol, phospholipids, free fatty acids) were also assessed. Student t test was employed for analysis. Membrane fluidity was lower in control fetal cells than in adults (p < 0.05) and lower in IUGR fetuses than in controls (p < 0.05). The mechanism may involve a low cholesterol concentration and a low unsaturated/saturated free fatty acids ratio in fetal blood cells membranes and plasma. Fetal cells membrane fluidity reflects in part fetal nutritional status.