2002 Science & Research Forum

Biosketch:

Joseph B. Stanford, MD, MSPH, CNFPMC, is Associate Professor in the Department of Family and Preventive Medicine at the University of Utah School of Medicine in Salt Lake City. He is Past President of the American Academy of FertilityCare Professionals. Dr. Stanford is a past recipient of the Generalist Physician Faculty Scholar Award from the Robert Wood Johnson Foundation. His current research in fertility care is funded by the National Institutes of Health. Co-authors: Ken R. Smith, PhD, Department of Family and Consumer Studies, University of Utah, Salt Lake City, David B. Dunson, PhD, Biostatistics Branch, National Institute of Environmental Health Sciences, USA

Presentation Abstract:

Vulvar Mucus Observations and the Probability of Pregnancy

Introduction: Standardized vulvar observation of cervical mucus discharge has been shown to correlate with biophysical parameters of endocervical mucus samples that influence sperm survival. The peak day of vaginal mucus discharge as assessed by vulvar observation has likewise been shown to correlate well with the timing of ovulation. However, data are limited regarding the correlation of vulvar mucus observations with the probability of pregnancy. We conducted this study to assess the day-specific and cycle-specific probabilities of pregnancy associated with the timing of intercourse and women’s daily observations of vaginal discharge, according to the established clinical observation and interpretation protocols of the Creighton Model FertilityCare System (CrMS).

Methods: Retrospective cohort study in the USA involving CrMS service programs in Missouri, Nebraska, Kansas, and California. Data were abstracted from women beginning use of the CrMS either to avoid pregnancy (avoiders, n=309) or to achieve pregnancy (achievers, n=117). Data included daily observations of women for vaginal mucus discharge, vaginal bleeding, intercourse, and clinically identified pregnancies. We used recently developed statistical methods to model day-specific and cycle-specific probabilities of pregnancy. The mucus cycle score (MCS) of Hilgers was used as a covariate to influence cycle-specific probability of pregnancy.

Results: Data were analyzed from 1681 cycles with 81 conceptions from avoiders and from 373 cycles with 30 conceptions from achievers. Non-negligible probabilities of pregnancy were present for avoiders from day -5 to day +3 relative to the peak day, and for achievers from day -3 to day +2. The highest probability of conception was on the peak day for both avoiders (about 40%) and achievers (about 10%). The cycle-specific probability of conception correlated strongly with the quality of mucus discharge as asssessed by MCS for avoiders but not for achievers. These trends remained after adjustment for age, parity, and recent use of oral contraceptives. There was a wide variety of underlying cycle-specific probabilities of conception, indicating substantial heterogeneity of fecundability in the population.

Conclusions: Standardized observations of vaginal mucus discharge made by women can be used clinically to identify the days with the greatest likelihood of conception from intercourse, whether they wish to achieve pregnancy or avoid pregnancy. There is a wide variability of fecundability (the potential for conception) among women learning and using the CrMS. The MCS may provide an indicator of the overall potential for conception in a given menstrual cycle.

Commentary:

Vulvar mucus observations and the probability of pregnancy

The mucus cycle score (MCS) is a quantitative method for scoring a woman's mucus cycle. This study looked at new users, so the question of normal versus abnormal fertility was not known in most cases. Although a practitioner or medical consultant can look at a chart and make some general observations, the MCS gives one the ability to look over a period of time and see changes from cycle to cycle. This is particularly helpful in patients with infertility problems that have limited mucus. The MCS allows us to see if the medical interventions that should help improve the mucus are actually working. Now why would the cycle- specific probability of conception correlate strongly with the MCS for avoiders but not for achievers?