How Do You Do a Fern Test

Examine the air-dried smear under the microscope without a coverslip and using low power magnification (10x magnification). I. Dried amniotic fluid produces a microscopically visible crystallization in a “fern” pattern. Dried normal vaginal fluid does not produce a “fern” pattern.

Why is a fern test done?

The fern test is most commonly used to provide evidence of the presence of amniotic fluid and is used in obstetrics to detect preterm premature rupture of membranes and/or the onset of labor. It also may provide indirect evidence of ovulation and fertility, although it does not predict the time of ovulation.

What gestational age can you see ferning?

Ferning occurs from 14 weeks of gestation onward Investigators obtained fluid samples by amniocentesis and confirmed that they were 100% nitrazine-positive.