Understanding the male and female biological clock

Age is an important independent factor that influences both female fertility and male fertility. However, the effect on female fertility is much more than compared to male fertility.

In women, biological age is the single most important factor that affects the chance of conceiving naturally.

Biological age also affects your chances of successful fertility treatment. Some studies in the last few years have reported the effect of age on sperm function.

Age and Female Fertility

It is well known that women are born with around 4-5 million eggs.

These eggs remain in dormant or quiet stage until the puberty. During this period, there is slow, but steady loss of the follicles. Only 400,000 – 500,000 follicles remain.

female-biological-clocThe process of decrease in quality and quantity of eggs continues at a slower pace. This reduction gathers pace around the age of 35 years and decreases even more rapidly in 40’s.

Women are most fertile in the third decade of their life or in their 20’s. This is the best age to try to conceive and have a family. It is called the ‘Golden period of female fertility’.  Some statistics about the female biological clock:

  • The chances of conceiving for a healthy woman in her 20’s is almost 25%
  •  This means every 1 out of four women trying naturally will achieve successful pregnancy within one menstrual cycle
  • Fertility starts declining from mid 30’s until they reach menopause (around 52 years)
  • For someone in early 40’s, this drops to 5%, which means only 1 in every 20 women will achieve a pregnancy
  •  This drops to almost negligible in women in mid-forties onward

In reality, the chances of conceiving are small for a large proportion of women, approximately 5-10 years before menopause.

It is important that you understand how your age might be affecting your fertility. As women grow older, the division process of the genetic material inside the egg cell becomes faulty.

With age, a large proportion of the eggs may have too few or too much of genetic material (chromosomes). This may lead to the genetically abnormal embryo, which can lead to either failure to conceive when trying naturally or failure of implantation during fertility treatment.

In a later age, this also leads to higher rate of miscarriage. Overall, women have a biological clock that ticks a lot faster than males.

Age and male fertility

There has been an increase in the average age at which men father children. This is from several social-demographic factors such as increased life expectancy, later marriages etc.

male-biological-clockThere are many studies that have looked into the effect of the advanced paternal age on fertility and reproductive outcomes.

Unlike women, there is a lack of consensus of the age beyond which advanced paternal age is defined. Also, the effect is not as drastic in men and is not significantly noticeable until the man is in his 60’s.

Though not as extreme as women, older men do experience changes in male fertility and sexual functioning with age. As men get older, they may notice several things happen:

  • That the testicles tend to get smaller and softer
  • Medical conditions that can affect the male fertility and sexual function
  • Decreased libido
  • Erectile dysfunction

The studies have shown some effects of advanced paternal age on male fertility and reproductive outcomes. This includes negative effects on sperm function such as low sperm count, low motility or low morphology, epigenetic changes, and DNA mutations.

These effects alone or in combination can lead to a decrease in ICSI or IVF success rate. It’s been reported that children fathered by men at later age may have higher incidence of autism, schizophrenia, bipolar disorders, certain hereditary birth defects, childhood leukaemia etc.