Positive Fern Test for the Rupture of Amniotic Membrane:
Amniotic fluid is released when the amniotic sac/membrane ruptures during labor or at term. This is also what we refer to when a pregnant woman's water breaks, usually spontaneously. If it occurs prior to term, it is referred to as premature rupture of the membranes. If a woman is near to or at or past her due date, a manual rupture of the amniotic sac may be performed to release the fluid if the membranes have not yet spontaneously ruptured. This is referred to as artificial rupture of the membrane.
An amniocentesis procedure is performed to draw amniotic fluid out for analysis. A fern test, as seen in the image above, is used to detect the "fernlike" pattern of cervical mucous to detect rupture of membranes and the onset of labor.