Odeblad, E. (1968). Biophysical composition of cervical mucus and spermigration during treatment with Conluten and Conlunett. Acta obstetricia et gynecologica Scandinavica, 47(S8), 7-19. https://doi.org/10.3109/00016346809156616
Odeblad E. Biophysical composition of cervical mucus and spermigration during treatment with Conluten and Conlunett. Acta obstetricia et gynecologica Scandinavica. 1968;47(S8):7-19. doi:10.3109/00016346809156616
Odeblad, E. "Biophysical composition of cervical mucus and spermigration during treatment with Conluten and Conlunett." Acta obstetricia et gynecologica Scandinavica, vol. 47, no. S8, 1968, pp. 7-19.
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How Birth Control Pills Change Cervical Mucus Type
This 1968 study followed 23 healthy women, ages 19 to 27. Each had one normal cycle, then one month on a combined birth control pill. Their cervical mucus switched from mostly fertile to mostly infertile within that first month, and sperm scores dropped too.
Key Findings
In the Conluten group, fertile-type mucus fell from 81% in the control cycle to 9% in the treated cycle. That 74-point drop was highly significant.
In the Conlunett group, fertile-type mucus fell from 79% in the control cycle to 15% in the treated cycle, a 64-point drop, also highly significant.
Sperm invasion and motility scores dropped alongside the mucus change. The author did not test this measure statistically. The difference rests on his judgment from years of experience.
The author estimated that cervical mucus probably becomes an effective barrier to sperm once fertile-type mucus drops to about 35% or less.
Interpretation
This is a small before-and-after study from 1968, without a randomized control group. Researchers watched the same 23 healthy women, ages 19 to 27, over one normal cycle and one treated cycle each. There was no long-term follow-up. Mucus type was measured objectively, with a lab technique that tracks water behavior in the mucus. One researcher scored the sperm test by hand, and it was not tested statistically, so treat it as descriptive. The findings show average changes in this one group during the first treated month. They do not set a fixed cutoff, and they may not apply beyond young, healthy, ovulating women.
RRM Context
This paper is part of Erik Odeblad's early work. He sorted cervical mucus into two types: fertile, estrogenic (E) type, and infertile, gestagenic (G) type. The classification underlies fertility awareness-based methods, such as the Billings Ovulation Method and the Creighton Model FertilityCare System. The methods teach women to spot these same mucus changes without a lab. The findings also show how combined hormonal birth control works. The pill pushes cervical mucus toward the G-type that blocks sperm. The shift is the same signal fertility-awareness charting is built to read.
Our editorial summary of this paper, not the article's abstract.
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