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Fern Test
Test CodeAlias/See Also
Preferred Specimen
Patient Preparation
Conditions for preparation of patient:
- Sterile speculum examination is performed to collect vaginal fluid.
- In equivocal cases, repeat the sterile speculum exam after the patient is in a recumbent position for one hour to determine if pooling of additional fluid in the vagina has occurred.
- In cases where gross fluid is notable on the perineum, peripad, or bedding, a slide can be obtained from that source.
Specimen Type: Direct smear made from vaginal fluid; allow to air dry at least 10 minutes. Only freshly obtained specimens should be used for testing. Obtain another specimen if the smear cannot be interpreted.
Instructions
Reference Range
Result Options:
Negative: No fernlike crystallization observered
Positive: Crystallization or a ferning pattern is observed
Clinical Significance
Detection of fern-type amniotic fluid crystallization is used as an aid in detection of ruptured amniotic membranes in pregnant patients. The test is often used in conjunction with vaginal pH.
Performing Laboratory
CRMC Perinatal POC department
Qualified physicians, nurse practitioners, physician assistants, and midwives may qualify. NOTE: residents and fellows with 2 years or more of residency training and a current California medical license may qualify.
Interns, residents and fellows enrolled in an ACGME approved training program may perform the Fern Test when supervised by a qualified, licensed provider.
Testing personnel are required to take the initial training and competency assessment. Competency assessment and initial training must be completed prior to patient testing. Competency assessment follows requirements for moderately complex testing.
