It’s a biological fact that for both men and women, fertility declines with higher age. So, the longer time a couple wait, the lower is their potential to conceive.
Several studies show that women younger than 35 and men younger than 40 have a better chance of getting pregnant. This goes both for natural pregnancies and with fertility treatments. So why is this?
Why does fertility drop with age?
Age is the single biggest factor affecting a women’s chance to conceive and have a healthy baby. Several scientific papers show that a women’s fertility starts to decline when she is in her early 30s, with the decline speeding up after 35 . The below figure (NHS statistics) illustrates the association between age and IVF birth-rate clearly. The higher the age, the lower the chance of live birth.
Unlike men, who continue to produce sperm throughout their lives, a woman is born with all the egg-containing follicles that she will ever have. The age-related decline in female fertility is therefore mainly because a few eggs are released from the ovaries every month. This leads to a decline in the total pool of eggs per cycle. Hormonal changes and a decline in both quality of eggs is also changing. Menopause is the time when menstrual periods stop permanently. The average age for menopause is 51. But most women become unable to have a successful pregnancy sometime in their mid-40s.
In contrast to the relatively abrupt changes that occur during female menopause, male reproductive function gradually declines during the aging process .
In general, scientific papers show that a decline in semen parameters appear to be mild with male aging, but that – still affects time to pregnancy .
Age and sperm quality
As men age, their testes tend to get smaller and softer resulting in a decline in sperm quality and production. These changes are partly because of an age-related decrease in testosterone level which plays a very important role in sperm production. Higher male age is not only associated with a decline in sperm production. It is also associated with increased sperm DNA fragmentation , worsened morphology (shape) and motility (movement). All these negative effects make the sperm cells less qualified for egg fertilization .
Furthermore, studies show that there is a higher risk of birth defects and some diseases like autism, cancer and schizophrenia when men are having children later in life. This is mainly due to increased amount of DNA mutations with age in men, but also to some extent to the higher DNA fragmentation rate.
– In case of infertility though 6 months and the age of the female partner is > 35, the couple should be referred to fertility specialist for fertility evaluation.
– If case of male age > 40 and infertility > 12 months, a sperm DNA fragmentation test could be considered.