Abstract: A test implement and method for colorimetrically assaying the quantity of N-acetyl-.beta.-glucosaminidase in a female biological medium, such as saliva, which quantity is indicia of fertility or pregnancy. The implement is an absorbent material, such as paper strip, impregnated with a phenolic derivative of N-acetyl-.beta.-d-glucosamine that reacts in the presence of the glucosaminidase at an acid pH to form a phenol that has a distinct color at an alkaline pH, and a buffer that maintains said acid pH. The method may be carried out by wetting the implement with the medium, alowing the phenol to form, raising the pH to alkalinity by wetting the implement with an appropriate buffer solution, and comparing the color of the implement with a color standard.