The fertile and infertile phases of the menstrual cycle are signaled by cervical-vaginal fluid die swell functions

Jian Wang, Stephen J. Usala, Faye O'Brien-Usala, William C. Biggs, Mark W. Vaughn, Gregory B. McKenna

Research output: Contribution to journalArticle

3 Scopus citations


Natural family planning is a method of fertility awareness based in part on detection of the fertile and infertile phases of the menstrual cycle through self-observation of cervical-vaginal secretions. Cervical-vaginal fluid (CVF) contains cervical mucus, a hydrogel that undergoes cyclic changes in viscoelasticity. We constructed a die swell device to study the viscoelastic properties and establish material functions of CVF samples that women obtain by self-aspiration. Two women for a total of 8 cycles provided day-specific CVF, urine and blood samples. Day-specific CVF samples were indexed to the day of ovulation (day 0) defined as the day of the luteinizing hormone peak. These samples were analyzed by extrusion through the die swell device and measurement of the subsequent flowgrams. Die swell ratio (B) was measured as the ratio, (maximum diameter of fluid swell after extrusion)/(inner die diameter), and die swell position (DisMax) was measured as the start position of maximum swell from the die orifice. These 2 rheological material functions, B and DisMax, were found to reliably correlate with the fertile and infertile phases of the cycle. This novel die swell device and methodology enables detection of viscoelasticity and therefore the presence of cervical mucus in CVF. Furthermore, it provides rheological measurements of cervical-vaginal secretions that correlate with the fertile and infertile phases of the menstrual cycle. The die swell device and methodology may serve as an aid for natural family planning.

Original languageEnglish
Pages (from-to)291-297
Number of pages7
Issue number6
StatePublished - Nov 1 2009



  • Cervical-vaginal fluid
  • Die swell
  • Fertility
  • Infertility
  • Menstrual cycle

Cite this