The age of a woman has a significant impact on both the number and quality of oocytes (eggs)available for fertilization. Here we discuss how age affects these crucial aspects of fertility:

1. Ovarian Reserve (Number of Oocytes) 

  • Number of Oocytes: Women are born with a definite number of oocytes they will everhave, typically around 1-2 million. This number decreases through out the reproductivelife of a woman due to a natural process called atresia, where eggs gradually degenerateand are absorbed by the body. 
  • Decline during the reproductive period: By puberty, the number of oocytes decreasesto about 300,000-500,000. Throughout a woman’s reproductive years, approximately300-500 oocytes will ovulate, and the rest will continue to die out. 
  • Accelerated Decline after mid 30s: There is rapid decline in the number of oocytes inthe mid-30s. By the time a woman reaches her late 30s to early 40s, the number ofoocytes declines sharply. 
  • Diminished Ovarian Reserve: Women in their 40s often have a significantly diminishedovarian reserve, leading to fewer oocytes available for ovulation or retrieval duringassisted reproductive techniques like IVF.

2. Oocyte Quality 

  • Chromosomal Abnormalities: As the women ages, the quality of oocytes declines,primarily due to an increase in chromosomal abnormalities. This is mainly because older oocytes have a higher likelihood of errors during meiosis, the process by which eggs are formed. 
  • Increased risk of Aneuploidy: Aneuploidy, where eggs have an abnormal number ofchromosomes, becomes more common with age. This can result in embryos that are notviable or that have genetic disorders such as Down syndrome. 
  • Mitochondrial Dysfunction: Aging oocytes often have diminished mitochondrialfunction, leading to lower energy production, which is crucial for cell division andembryo development.

3. Impact on Fertility and Pregnancy 

  • Decreased Fertilization Rates: as the quality of the oocyte becomes poor with age thereis fall in the fertilization rates. Even when fertilization occurs, the likelihood of a normalembryo development and implantation is reduced. 
  • Higher Miscarriage Rates: The risk of miscarriage increases with age, mainly due to thehigher incidence of chromosomal abnormalities in the oocytes. 
  • Reduced Pregnancy Rates: The overall chances of achieving a successful pregnancydecline with age, reflecting both the reduced quantity and quality of oocytes.

4. Assisted Reproductive Technologies (ART) 

  • IVF Success Rates: In vitro fertilization (IVF) success rates are closely tied to the age ofthe woman, as both the number of retrieved oocytes and their quality influence thelikelihood of successful fertilization and pregnancy. Younger women generally havehigher success rates compared to older women. 
  • Use of Donor Eggs: For older women or those with significantly diminished ovarianreserve and oocyte quality, using donor eggs from younger women can substantiallyincrease the chances of a successful pregnancy. Donor eggs tend to have higher qualityand lower rates of chromosomal abnormalities as the eggs are taken from youngerfemales.

5. Hormonal Changes and Ovarian Response 

  • Decreased Hormonal Response: As women age, their ovaries become less responsive togonadotropins (hormones used in fertility treatments to stimulate the ovaries). This canresult in fewer oocytes being retrieved during IVF cycles. 
  • Increased FSH Levels: Elevated baseline levels of follicle-stimulating hormone (FSH)are common in older women, indicating reduced ovarian reserve. High FSH levels canalso reflect poorer oocyte quality.

Conclusion

The age of a woman has a profound impact on both the number and quality of her oocytes, withsignificant implications for natural fertility and the success of assisted reproductive technologieslike IVF. As women age, the decline in ovarian reserve and oocyte quality leads to lowerfertilization rates, higher miscarriage rates, and reduced overall chances of pregnancy.Understanding these age-related changes is crucial for fertility planning and treatment. Womenwho are concerned about their fertility due to age should consult with a reproductive specialist toexplore their options and optimize their chances of achieving a successful pregnancy.