Test Overview
Test Methodology

Provider performed microscopy. The fern test is based on the ability of amniotic fluid to form a microscopic crystalline pattern that resembles fern leaves when the fluid air dries on a glass slide.

Test Usage

Performed by authorized providers in the point of care. Used to assess for premature amniotic fluid leakage: i.e. PROM (Premature Rupture of Membranes) or PPROM (Preterm Premature Rupture of Membranes).

Reference Range *


* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

•Cellar debris and blood in the sample may inhibit crystallization of amniotic fluid, and cause a false negative.
•"Ferning" is not specific for amniotic fluid. Other fluids (e.g., blood cervical mucus, semen and some urine specimens) when dried can also yield microscopic crystallizations in a "fern" pattern, and cause false positives.
•Prolonged rupture of membranes (greater than 24 hours) or slow, minimal leaks can yield false negative results.

Test Details
Soft Order Code
MiChart Code
Fern Test, Point of Care
Point of Care
Point of Care
Specimen Requirements
Collection Instructions

1. A sterile speculum is placed into the vagina. A lubricant or antiseptic should not be used as these substances will affect ferning.
2. Using a sterile cotton swab, obtain sample of vaginal secretions from the posterior vagina where fluid has pooled. Do not touch the mucus plug on cervix.

Rejection Criteria
If lubricants and antiseptics are used during the collection of the sample, the sample is to be rejected.
Additional Information

For more test specific information, please refer to the test procedure found on the Michigan Medicine POC website: https://www.pathology.med.umich.edu/point-of-care

CPT Code
pH (72269-4), Ferning (54452-8)