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The timing of the “fertile window” in the menstrual cycle: day specific estimates from a prospective study

BMJ 2000; 321 doi: https://doi.org/10.1136/bmj.321.7271.1259 (Published 18 November 2000) Cite this as: BMJ 2000;321:1259

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Starting point for more efficient NFP

Dear Sir,

To your fundamental question: "Can we dependably and
accurately predict ovulation six days before it occurs?" we
can try to answer starting with the studies of Billings et
al. (1972), Flynn & Linch (1976), Hilgers et al. (1978).

In 1979 we undertook a study to verify the effective ability
of a selected group of young Italian women to recognize and
interpret the cyclic changes in their cervical mucus
according the guidelines of the Ovulation Method of NFP
described by Billings (OMB). None of them had previously
used contraceptives. The results were published on
'Contraception' 1981.

Through the hormonal-symptomatic correlations we found that
the mean number of mucus days preceeding ovulation was 6.0,
which agrees almost exactly with the figure arrived at in
three quoted studies.

The close correlation between the onset of the mucus symptom
and the level of circulating estradiol-17 beta, and between
the peak symptom and the circulating LH peak clearly
establishes that the subjective recognition of a typical
mucus pattern accurately mirrors the hormonal events
associated with the process of ovulation and may be utilized
as a simple, reliable method for identyfing the potentially
fertile window of the cycle independently to its regularity.

From that time my experience as Billings RNF Method teacher
and regional coordinator of the Veneto OMB-Teachers in Italy
continues to testify the practical validity of the proved
assumpions.

On the basis of the quoted studies and experiences I hope
your researches in this field can contribute "for more
efficient NFP".

With all good wishes,

Prof. Sergio Cortesi

References.

Billings EL, Billings JJ, Brown JB, Burger HG. Symptoms and
hormonal changes accompanying ovulation. Lancet 1972;1:282

Flynn AM, Lynch SS. Cervical mucus and identification of the
fertile phase of the menstraul cycle. Brit.J.Obstet.Gynecol.
1976;83:656

Hilgers TW, Abraham GE, Cavanagh D. Natural Family Planning.
I. The peak symptom and estimated time of ovulation.
Obstet.Gynecol. 1978;52:575

Cortesi S, Rigoni G, Zen F, Sposetti R. Correlation of
plasma gonadotrophins and ovarian steroid pattern with
symptomatic changes in cervical mucus during the menstrual
cycle in normal cycling women. Contrception 1981;23:629

Cortesi S. Physiological markers of fertility.
It.J.Clin.Chem. 1983;8:277

Cortesi S, Fortunato A, Marzot E, Soffiati G. Simultaneous
dosage of oestrone-3-glycuronide and
pregnandiol-3-glycuronide in urines to monitor the fertile
period in the w

Competing interests: No competing interests

30 November 2000
Sergio Cortesi
Retired Director Clinical Chemistry Lab-Regional Hospital Vicenza (Italy)nal HospitalRe