BACKGROUND AND PURPOSE:

• Shortening menstrual cycle length (MCL) may be a useful biomarker for reduced ovarian reserve
• Younis et al. (Human Reproduction Update, 2020) examined the association between shortened MCL in regularly cycling women and ovarian reserve

METHODS:

• Systematic review and meta-analysis
• Data sources
  • PubMed | Web of Science | Trip | EBSCO | ClinicalTrials.gov | Cochrane library (between January 1978 and August 2019)
• Definitions
  • Long MCL: 32 to 35 days
  • Shortened MCL: 21 to 27 days
  • Normal MCL: 28 to 31 days
  • All other MCL: 28 to 35 days  
• Inclusion criteria
  • Prospective and retrospective studies
  • Studies that explored an association between MCL and proxies of ovarian reserve
  • Excluded Studies: PCOS | Ovarian failure | Oral contraception treatment | Prior chemotherapy | Ovarian surgery
• Primary outcomes
  • Determine whether there is a relationship between MCL and ovarian reserve tests, fecundability in natural cycles, and IVF outcomes

RESULTS:

• 11 studies | 12,031 women
  • Included studies had a low risk of bias
• Short MCL was associated with lower ovarian reserve values compared with all other cycle lengths
• Compared to normal MCL, AMH levels were significantly lower in short MCL
  • Estimated weighted mean difference (WMD) −1.3 ng/mL (95% CI, −1.75 to −0.86; P<0.001)
• Compared to normal MCL, antral follicle values were significantly lower in short MCL
  • WMD −5.17 (95% CI, −5.96 to −4.37; P<0.001)
• Fecundability was lower in women with short MCL
  • Odds ratio (OR) 0.81 (95%, CI 0.72 to 0.91; P<0.001)
• In IVF settings, fewer oocytes were retrieved in short MCL
  • Estimated WMD −1.8 oocytes (95% CI, −2.5 to −1.1; P<0.001)
• Clinical pregnancy rate was lower for women with short MCL
  • Overall OR 0.76 (95% CI, 0.60 to 0.96; P=0.02)

CONCLUSION:

• For women with regular cycles, MCL is closely associated with ovarian reserve biomarkers during reproductive years
• A short MCL is associated with reduced ovarian reserve, reduced fecundability, and worse IVF outcomes
• The authors suggest

…that short MCL may be a sign of ovarian aging, combining the quantitative and qualitative facets of ovarian reserve

Educational efforts ought to be designed to guide women with short MCL at a young age, who desire children in the future, to seek professional counselling

Learn More – Primary Sources:

Does an association exist between menstrual cycle length within the normal range and ovarian reserve biomarkers during the reproductive years? A systematic review and meta-analysis

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