Age is the single most important factor affecting a woman’s fertility. While advances in reproductive medicine have expanded options for couples trying to conceive later in life, understanding the biological reality of age-related fertility decline helps in making informed decisions about family planning.
Female Fertility and Age
Women are born with all the eggs they will ever have – approximately 1–2 million at birth. By puberty, this number declines to about 300,000–400,000. Each month, a group of eggs begins to develop, but only one typically matures and is released. The rest are lost. This gradual decline accelerates significantly after age 35.
- Under 30: Peak fertility. Approximately 20–25% chance of conception per menstrual cycle.
- 30–35: Gradual decline begins. Monthly conception rate drops to about 15–20%.
- 35–40: More noticeable decline in both egg quantity and quality. Monthly conception rate approximately 10–15%.
- Over 40: Significant decline. Monthly conception rate drops to about 5% or less. Miscarriage rates increase substantially.
Why Does Egg Quality Decline?
As women age, eggs are more likely to have chromosomal abnormalities. This leads to lower fertilisation rates, higher rates of failed implantation, increased miscarriage risk, and a greater chance of chromosomal conditions such as Down syndrome. This decline in egg quality is the primary reason fertility decreases with age, and it cannot be reversed.
Male Age and Fertility
While male fertility declines more gradually than female fertility, age does matter for men too. After age 40, men may experience decreased sperm quality and DNA integrity, longer time to achieve pregnancy, slightly higher risk of genetic conditions in offspring, and reduced testosterone levels. However, men can often father children well into their later years, unlike the more definitive timeline for women.
Options for Older Couples
- IVF: Can help overcome many age-related barriers, though success rates decline with maternal age.
- PGT-A (Preimplantation Genetic Testing): Screening embryos for chromosomal abnormalities before transfer can improve success rates in older women.
- Egg freezing: Women who freeze eggs at a younger age can use them later with success rates reflecting the age at freezing.
- Donor eggs: For women with significantly diminished ovarian reserve, using donor eggs from a younger woman offers high success rates.
If you are over 35 and have been trying to conceive for 6 months without success, or if you are over 40, seeking a fertility evaluation sooner rather than later gives you the best chance of a successful outcome. Time is an important factor, and early intervention can make a significant difference.