STUDY QUESTION

What are the characteristics of, and how variable are, individual normal menstrual cycle profiles of excretion rates for the urinary metabolites oestrone glucuronide (E1G) and pregnanediol glucuronide (PdG)?

SUMMARY ANSWER

There is a continuum of menstrual cycle profiles that differ from standard textbook profiles but which can be understood simply in terms of growth, atresia and ovulation of ovarian follicles.

WHAT IS KNOWN ALREADY

Point-of-care assays with the Ovarian Monitor pre-coated assay tubes, using urine samples diluted to a constant volume per unit time, give laboratory accurate clinical data for individual menstrual cycles. Lay operators can perform the point-of-care assay system at home to achieve reliable and reproducible results, which can be used for natural family planning.

STUDY DESIGN, SIZE, DURATION: This prospective study involved 62 women, with normal menstrual cycles, recruited from three centres: Palmerston North, New Zealand, Sydney, Australia and Santiago, Chile. The study lasted 3 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Women collected daily urine samples and determined their E1G and PdG rates with a pre-coated enzyme assay system known as the Ovarian Monitor. For two cycles, the assays were repeated in a study centre and the results were averaged to give 113 individual menstrual cycles for analysis. The cycles were displayed individually in a proprietary database program.

MAIN RESULTS AND THE ROLE OF CHANCE

The individual normal hormonal profiles were more complex than the classic composite curves for 40% of the cycles. Of 113 ostensibly normal cycles, only 91 were potentially fertile and 22 had some luteal phase defect. The oestrone glucuronide and PdG excretion rates were reliable and informative in the non-invasive elucidation of ovulation and ovarian function for both simple and complex profiles. Daily monitoring revealed the variability of normal menstrual cycle profiles. The LH peaks were variable and ambiguous markers for ovulation.

LIMITATIONS, REASONS FOR CAUTION: The study consisted of cycles only from women with regular cycles of 20-40 days duration. All the women were intending to avoid a pregnancy during the study thus the limits of the fertile window were not tested.

WIDER IMPLICATIONS OF THE FINDINGS

The principles established in this study should apply to cycles of any length. All peaks in oestrone glucuronide excretion should be tested by concurrent measurements of PdG, which gives a positive indication of the fate of the follicle it represents. The Ovarian Monitor provides a useful addition for practitioners of natural family planning.

STUDY FUNDING/COMPETING INTEREST(S): Financial support for this study was obtained from the UNDP/UNFPA/World Bank/WHO Special Programme of Research, Development and Research Training in Human Reproduction (HRP). D.G.C. is currently employed by and holds stock in Manawatu Diagnostics Ltd, a company in the development phase of a potentially competing product. The remaining authors have nothing to declare.