How much do chances of pregnancy decrease during perimenopause?

Fertility Decline During Perimenopause

Fertility decreases significantly during perimenopause, with chances of natural conception dropping by approximately 50% by the mid-forties and approaching near-zero by age 50. 1

Understanding Perimenopause and Fertility

Perimenopause marks the transition from normal ovulation to anovulation, ultimately leading to permanent loss of ovarian function. This transition affects fertility in several ways:

• Age-Related Fertility Decline:

  • Fertility begins declining gradually from age 30
  • More pronounced decline between ages 35-40
  • Dramatic decrease after age 40
  • Age 41 is considered the approximate point when fertility significantly diminishes 1

• Biological Mechanisms of Reduced Fertility:

  • Diminished ovarian reserve (fewer remaining eggs)
  • Decreased egg quality with higher rates of chromosomal abnormalities
  • Declining endocrine function of the ovaries
  • Changes in menstrual cycle regularity and ovulation patterns

Quantifying the Fertility Decline

The fertility decline during perimenopause is substantial:

• Fecundity (monthly probability of conception) decreases by half as early as the mid-forties 2
• Spontaneous conception rates become minimal in perimenopausal women 1
• Even with assisted reproductive technologies, success rates are very poor in women of advanced reproductive age 1

Pregnancy Risks During Perimenopause

Despite reduced fertility, unintended pregnancies still occur in perimenopausal women at ratios similar to younger women 3. These pregnancies carry increased risks:

• Higher rates of maternal complications
• Increased risk of miscarriage
• Greater likelihood of chromosomal abnormalities 3
• Higher risk of pregnancy loss due to diminished ovarian reserve 4

A meta-analysis showed that women with diminished ovarian reserve (measured by low AMH levels) have:

• 28% higher risk of miscarriage in women under 35 (OR 1.28; 95% CI, 1.07-1.53)
• 85% higher risk of miscarriage in women over 35 (OR 1.85; 95% CI, 1.35-2.52) 4

Contraception During Perimenopause

Due to the continued possibility of pregnancy, contraception remains important during perimenopause:

• Reliable contraception should be used until menopause is confirmed by:

  • Cessation of menses for 2 years prior to age 50
  • Cessation of menses for 1 year after age 50
  • Two elevated FSH values ≥20-30 IU/L while off hormonal methods 3

• Sterility cannot be assumed until at least age 60, as spontaneous pregnancies have been reported in women up to age 59 3

Common Symptoms and Management During Perimenopause

Perimenopause is associated with several symptoms that can affect quality of life:

• Hot flashes (experienced by most women, moderately to severely problematic for about 1/3)
• Poor sleep quality
• Increased anxiety and depressed mood
• Vaginal dryness and dyspareunia (affecting about 1/3 of women) 5

Conclusion

The perimenopause represents a significant transition period with substantial reduction in fertility. While natural conception becomes increasingly unlikely with advancing age through perimenopause, women should be aware that pregnancy remains possible until menopause is confirmed, and any pregnancies that do occur carry higher risks of complications and genetic abnormalities.