Selected physicochemical properties of amniotic fluid according to week of pregnancy

A hundred years ago, scientists believed that amniotic fluid is a yellowish hypotonic mixture of foetal urine and maternal transudate with peculiar odour. Current knowledge shows that it represents a dynamic, complex mixture of inorganic and organic compounds.

Despite modern technological procedures, information is still lacking about the composition and properties of amniotic fluid. We focused on dynamics of selected physical and chemical properties of the amniotic fluid with the increasing gestational week.

The physicochemical characteristics of 89 amniotic fluid samples were determined according to the week of pregnancy. The determination of pH, specific gravity, glucose and nitrites was performed immediately, at room temperature.

Our results show a significant negative correlation between week of pregnancy and semi-quantitative determined parameters of specific gravity (p < 0.001), pH (p < 0.01) and glucose (p < 0.001) values. Within the whole group of samples (n = 89), 29 % (n = 26) were nitrites positive (N+) and 71 % (n = 63) nitrites negative (N-).

In this study were determined basic parameters of amniotic fluid, which could be related to a wide range of pathological states (Tab. 2, Fig. 1, Ref. 27).