Fern Test - Amniotic Fluid Crystallization Test     
MCL Procedure for Waived Applications         effective 8/17/02

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Specimen:  Vaginal swab obtained from the posterior vaginal pool.
- avoid the use of any lubricants or antiseptics
- use a sterile swab and do not touch the mucus plug
- prepare a thin smear on a glass microscope slide by spreading evenly.

Testing: 

• Allow the slide to air dry- do not apply heat and do not coverslip the slide.
• Examine the fully-dried slide microscopically, using the 10X objective
• Observe for "fern-like" crystals. Presence of crystals indicates that the fluid is amniotic fluid.
• Record the results: Write your name, the date, time and findings on the patient record.

Positive Fern Test- note crystal formations	Negative Fern test- no "fern-like" cytstals

Interfering Substances/ limitations:
If present, blood, urine or cervical mucus can result in a false positive finding.
False negative findings can result from prolonged rupture of membranes (>24 hr).

 Quality control:

• Follow the procedural instructions exactly.
• There are no external(nor internal) quality controls  to be performed at the unit level.

Images courtesy of University of Texas Medical Branch- POCT team. Used with permission.