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Fern Test
MessageHematology
Test Code
LAB5210278
Alias/See Also
Ruptured membranes, Amniotic Fluid Crystallization test
CPT Codes
87210
Preferred Specimen
Well-dried slide prepared from vaginal fluid
Instructions
Slides are collected in the perinatal area by either the Physician or TNs trained in this procedure. Vaginal fluid from the posterior Fornix area is collected by swab and spread on a clean dry slide. The swab is to be rolled on the smear, spreading the specimen thinly over at least two-thirds of the slide and allowed to dry for at least 15 minutes.
Specimen and smears are to be collected using Universal Precautions.
Slides are to be labeled with the patient last name and medical record number and placed into a collection container.
Specimen and smears are to be collected using Universal Precautions.
Slides are to be labeled with the patient last name and medical record number and placed into a collection container.
Specimen Stability
Ambient
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
No Label / Mis-Label
Methodology
If cervical mucus is aspirated, spread on a glass slide, allowed to dry for a few minutes, and examine microscopically, characteristic patterns can be discerned that are depended on the stage of the ovarian cycle and the presence or absence of pregnancy. From about the 7th day of the menstrual cycle to about the 18th day, a fern-like pattern of dried cervical mucus is seen; it is sometimes called a process of "arborization" or the "palm leaf pattern." After approximately the 21st day, this fern pattern does not develop, but rather there is a quite different pattern that forms, i.e., a beaded or cellular appearance. This beaded pattern usually also in encountered in pregnancy. The crystallization of the mucus, which is necessary for the production of the fern, or arborized pattern, is dependent upon the concentration of electrolytes, principally sodium chloride, in the secretion. In general, a concentration of sodium chloride of 1% is required for the full development of a fern patter; below that concentration, either a beaded pattern or atypical incomplete arborization is seen.
Report Available
Same day
Limitations
Ferning patterns may be missed if smears are not completely dry or if the smear is not adequately scanned
If the cervical os is touched with cotton-tipped applicator during sample collection, the secretion can appear to fern even with membranes are intact.
Ruptured of the membranes may happen at any time during pregnancy. It becomes a problem if the fetus is premature (preterm rupture of membranes) or, in the case of a mature fetus, if the period of time between rupture of the membranes and the onset of labor is prolonged (prelabor rupture of the membranes). If 24 hours elapse between rupture of the membranes and the onset of labor the problem is one of prolonged premature ruptures of the membrane.
If the cervical os is touched with cotton-tipped applicator during sample collection, the secretion can appear to fern even with membranes are intact.
Ruptured of the membranes may happen at any time during pregnancy. It becomes a problem if the fetus is premature (preterm rupture of membranes) or, in the case of a mature fetus, if the period of time between rupture of the membranes and the onset of labor is prolonged (prelabor rupture of the membranes). If 24 hours elapse between rupture of the membranes and the onset of labor the problem is one of prolonged premature ruptures of the membrane.
Reference Range
Not Present
The amniotic fluid crystallization test may be false negative in the presence of blood, meconium, and heavy discharge; and false positive with cervical mucus (which crystallizes in 5 to 30 percent of all pregnancies).
The amniotic fluid crystallization test may be false negative in the presence of blood, meconium, and heavy discharge; and false positive with cervical mucus (which crystallizes in 5 to 30 percent of all pregnancies).
Clinical Significance
Premature rupture of the membranes during pregnancy is an important cause of premature labor, prolapse of the cord, and intrauterine infection. The fern test is used in conjunction with a nitrazine pH paper test to confirm the presence of amniotic fluid into the cervix from a ruptured membrane.
Performing Laboratory
HHN / HHI Laboratory
