The fern test is a medical laboratory test used in

obstetrics Obstetrics is the field of study concentrated on pregnancy, childbirth and the postpartum period. As a medical specialty, obstetrics is combined with gynecology under the discipline known as obstetrics and gynecology (OB/GYN), which is a su ...

and

gynecology Gynaecology or gynecology (see American and British English spelling differences) is the area of medicine concerned with conditions affecting the Female reproductive system, female reproductive system. It is often paired with the field of obste ...

. The name refers to the detection of a characteristic "

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

like" pattern of vaginal secretions when a specimen is allowed to dry on a glass slide and is viewed under a low-power microscope. The fern test is most commonly used to provide evidence of the presence of

amniotic fluid The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products betwee ...

and is used in obstetrics to detect preterm

premature rupture of membranes Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labour. Women usually experience a painless gush or a steady leakage of fluid from the vagina. Compl ...

and/or the onset of labor. It also may provide indirect evidence of

ovulation Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and ...

and fertility, although it does not predict the time of ovulation.Patrick Duff, MD (2016). "Preterm premature (prelabor) rupture of membranes". In Vanessa A Barss, MD, FACOG (Ed.), ''uptodate'' Retrieved from http://www.uptodate.com/ Ferning was first described in the field of gynecology in 1945 by

Georgios Papanikolaou Georgios Nikolaou Papanikolaou (or George Papanicolaou ; ; 13 May 1883 – 19 February 1962) was a Greek physician, zoologist and microscopist who was a pioneer in cytopathology and early cancer detection, and inventor of the pap smear for d ...

, inventor of the

pap smear The Papanicolaou test (abbreviated as Pap test, also known as Pap smear (AE), cervical smear (BE), cervical screening (BE), or smear test (BE)) is a method of cervical screening used to detect potentially precancerous and cancerous processes in ...

, as a test for ovulation during a normal

menstrual cycle The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The ovarian cycle controls the production and release of eg ...

. When high levels of

estrogen Estrogen (also spelled oestrogen in British English; see spelling differences) is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three ...

are present, such as just before ovulation (or during pregnancy), the cervical mucus forms fern-like patterns due to crystallization of sodium chloride on mucus fibers. This pattern is known as arborization or 'ferning'. When

progesterone Progesterone (; P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the ma ...

is the dominant hormone, as it would be in the second half of a normal cycle, the fern pattern is no longer discernible, and the pattern is completely absent by the 22nd day of a woman's cycle after ovulation (assuming a 28 day cycle). The disappearance of the fern pattern after the 22nd day suggests ovulation, and its persistence throughout the menstrual cycle may suggest an anovulatory cycle.Moghissi, S. (2003
"Documentation of Ovulation"
In Sciarra, J. ''Gynecology and Obstetrics'', CDROM edition. Ferning is now most commonly used as a test for prelabor rupture of membranes which refers to the rupture of the amniotic sac during pregnancy. The sodium chloride content of amniotic fluid secreted by the fetal kidneys may be indicative that membrane rupture has occurred, though the pattern of 'ferning' seen in amniotic fluid is distinct from that seen in cervical mucus. Amniotic fluid tends to produce a more delicate pattern, compared to a thick and wide arborization pattern seen in dried cervical mucus.

False positive A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resu ...

results are mostly attributable to cervical mucus, though have been reported due to semen and fingerprints, while false negatives are attributable to inadequate fluid available at the time of specimen collection, or contamination from leukorrhea, blood or meconium. Additionally, the accuracy of ferning is markedly less in women who are not in labor as compared to those in labor, with a reported sensitivity and specificity of 51% and 70%, respectively, in patients without labor and 98% and 88%, respectively, in patients in labor.

References

{{Reflist Medical tests Gynaecology