Saliva containing high estrogen hormones can form a ferning picture on saliva dried on object glass.
Riska Mutia Ersyari, Rosiliwati Wihardja, Murnisari Dardjan 2014, 'Determination of ovulation in women using saliva ferning test', Padjadjaran Journal of Dentistryhttp://jurnal.unpad.ac.id/pjd/article/view/14011. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)