Unexplained infertility is defined as conception delay without any identifiable cause. However, even the most sophisticated diagnostic tests cannot identify all the potential contributory factors.
With advancing age of a woman, the egg quality and reserve declines. Due to age-related changes in the egg quality, the risk of chromosomal abnormality increases in the embryo and that leads to failure of implantation and increase in the rate of miscarriage.
Hence there is a decline in fertility with an increase in female age and this is seen particularly after the age of 35 years. Women with regular periods and confirmed ovulation can still experience reduced fertility due to deterioration of egg quality with age.
Unfortunately, there are no tests to assess the egg quality. Age alone is considered to be a surrogate marker for egg quality. Higher the age of the women, lower is her egg quality[Ref].
Male age also has an impact on fertility potential. Though there is no clear threshold like women, the sperm quality is found to decline after 40-45 years of age [Ref].
While it is impossible to stop the ageing process, both men and women can protect their fertility from ageing process by improving general health, eating more balanced diet, avoiding smoking or drinking too much alcohol/caffeine and doing mild to moderate exercise to maintain a healthy BMI of 20-25.