Ferning and spinnbarkeit tests for ovulation

The cervical glands proliferate under the influence of oestrogen secreted during the follicular stage of the ovarian cycle . The glands become longer as the follicular cycle progresses. The glandular epithelial cells become larger and start to secrete a mucus that is initially thick and viscous.

Under the influence of estrogen, and as the time of ovulation approaches, the quality of the cervical mucus begins to change. From about the 10th day of the cycle till ovulation on the 14th - 16th day, the mucus becomes profuse, more watery and tenacious. It begins to resemble egg-white - clear, profuse, and slippery.



Cervical Mucus at Ovulation

The mucus becomes so tenacious that it can be stretched in threads up to 10-15cm long at the time of ovulation. This quality of the mucus is called 'spinnbarkeit' and is used for the thread test to diagnose ovulation.

The amount of cervical mucus may be so profuse as to be termed the 'vaginal cascade'. This watery cervical mucous helps the sperm to swim into the uterus to fertilize the ovum.

During this time, if the cervical mucus is collected on a clean glass slide and is allowed to dry, it will form a characteristic pattern that resembles the fronds of a fern. This can be observed under a microscope and is known as 'ferning'or the 'fern test'. It is another important diagnostic criteria of ovulation. Ferning can be seen from the 6th to the 22nd day of the cycle.


Fern Test at Ovulation

The amount and character of the cervical mucous is an important diagnostic criteria for ovulation in cases of infertility.