Fern Test for Rupture of Membranes

Abbrev Code:FERN   
Order Code:LAB4194Order Name:Fern Test for Rupture of Membranes
Synonyms:Fern Crystallization; Rupture of Membranes (ROM)
CPT Codes: Q0114 x

Collection Instructions

Specimen:Fluid, cervical or amniotic
Optimal Volume:microscope slide swabbed with fluids
Container:Microscope slides
Collection Instructions:
  1. Place the patient in right or left lateral position to allow pooling of any amniotic fluid.
  2. Insert sterile speculum using sterile technique. DO NOT warm speculum or use any lubricant.
  3. Use spotlight or flashlight to view cervix and check for pooling of liquid.
  4. Swab area near the cervical OS using sterile Q-tip. If pooling liquid is present, saturate Q-tip with fluid. Avoid touching the vaginal wall and cervix.
  5. Spread the collected fluid that adheres to the swab over microscope slides. Apply a thin layer for best results. Allow slide to air dry (do not apply coverslip). Only handle slide with gloves, as fingerprints may give false results or interfere with interpretation.
  6. Remove speculum. Reposition patient.

Processing and Shipping

Test Performed at or Referral Lab Hematology  (Clinics, Grand Itasca, Lakes, Northland, Range, Ridges, Southdale, St. John's, UMMC/UMMCH-West Bank, Woodwinds)


Reference Range:


Nitrazine pH:


Probably membranes are not ruptured.


Probably membranes are ruptured.


May be due to blood or cervical mucus


Fern Crystallization:

Positive result

Fern pattern, i.e. palm leaf pattern is observed when amniotic fluid crystallizes as it dries on a glass surface. Observation of a fern pattern indicates the presence of amniotic fluid.

Negative result

Beaded or cellular appearance of cervical mucus.



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