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The normal variabilities of the menstrual cycle
Laurence A Cole1, Donald G Ladner, Francis W Byrn
1Department of Obstetrics and Gynecology, University of New Mexico, Albuquerque, NM 87131, USA. Larry@hcglab.com
Fertility and Sterility
|April 25, 2008
Summary
This study establishes normal ranges for menstrual cycle variability using advanced testing, providing crucial data for clinical practice and identifying a distinct 10-day window for implantation.
Area of Science:
- Reproductive Endocrinology
- Gynecology
- Clinical Diagnostics
Background:
- Menstrual cycle variability presents challenges in clinical interpretation.
- Newer diagnostic methods offer opportunities to refine understanding of normal cycle parameters.
Purpose of the Study:
- To establish normal ranges for menstrual cycle variability using advanced testing.
- To resolve discrepancies in existing data regarding cycle timing and implantation.
Main Methods:
- Prospective analysis of daily urine samples from 167 women seeking pregnancy.
- Measurement of luteinizing hormone (LH) and human chorionic gonadotropin (hCG) levels.
- Evaluation of 458 non-gestational and 111 gestational cycles.
Main Results:
- Average menstrual cycle length was 27.7 ± 2.4 days.
- The LH surge, indicating the ovulatory window, occurred at 14.7 ± 2.4 days.
- Implantation, detected by hCG, occurred at 24.6 ± 3.1 days, 4.3 days before the expected menses.
Conclusions:
- Findings align with epidemiological and hormonal data on cycle length and ovulation timing.
- Implantation occurs within a defined 10-day interval, challenging prior variance data.
- Established reference ranges aid in distinguishing normal from abnormal menstrual cycles.
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