Ferning
Definition
The arborisation pattern formed when cervical or vaginal mucus dries on a glass slide, produced by sodium chloride and glycoprotein crystallisation. Visible by light microscopy; most pronounced mid-cycle. A presumptive indicator of vaginal or cervical mucus.
- Cause
- Sodium chloride and glycoprotein crystallisation
- Detection
- Light microscopy on a dried slide
- Timing
- Most pronounced mid-cycle
- Evidentiary status
- Presumptive indicator only
Common questions
Why is ferning only a presumptive test rather than confirmatory?+
The pattern depends on estrogen-driven electrolyte and glycoprotein levels, so it varies across the menstrual cycle and can be weak or absent at other times, and it is not specific enough to a single body fluid to confirm origin on its own.
What happens to ferning quality outside mid-cycle?+
The pattern becomes less distinct or fails to form, because the salt and glycoprotein concentrations that drive crystallisation drop after ovulation, which limits when a clear positive result can be expected.
Related terms
- Ehrlich's Reagent
- A solution of para-dimethylaminobenzaldehyde in acid. It reacts with urobilinogen and related pyrrole-containing compounds to produce a pink-red colour, used as a...
- Glycogen
- A polysaccharide energy store present in vaginal epithelial cells. It is released when cells are lysed and can be detected by periodic...
- Periodic Acid-Schiff (PAS) Reaction
- A histochemical staining method that oxidises polysaccharides (including glycogen) to produce aldehydes, which are then detected by Schiff reagent as a magenta...
- RSID-Vaginal Mucosa
- Rapid Stain Identification of Vaginal Mucosa. An immunochromatographic lateral-flow assay using antibodies targeting proteins specific to human vaginal epithelial cells, providing higher...
- Urobilinogen
- A colourless bile pigment metabolite produced by intestinal bacteria from bilirubin. It is excreted in faeces (as urobilin/stercobilin) and detected in forensic...