It’s a biological fact that for both men and women, fertility declines with age. So, the longer time a couple waits, 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 does fertility drop with age?
Age and Fertility for women
Age is the single biggest factor affecting a woman’s chances of conceiving and giving birth to a healthy baby. Several scientific papers show that a woman’s fertility starts to decline when she is in her early 30s, with the decline speeding up after 35 . The below figure clearly (NHS statistics) illustrates the association between age and IVF birth-rate. The higher the age, the lower the chances of a live birth.
Men continue to produce sperm throughout their lives. Unlike men, a woman is born with all the egg-containing follicles that she’ll ever have. The age-related decline in female fertility is therefore mainly because a few eggs are released from the ovaries every month. Due to hormonal changes, this leads to a decline in the total pool of eggs per cycle. It also leads to a decline in the quality of those eggs. Menopause is the time when menstrual periods stop permanently. The average age for menopause is 51. However, most women become unable to have a successful pregnancy sometime in their mid-40s.
Age and fertility for Men
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 this 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’s also associated with the negative effects of 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 like autism, and some diseases like cancer and schizophrenia when men have children later in life. This is mainly due to an increased amount of DNA mutations with age, but also (to some extent) to the higher DNA fragmentation rate.
Recommendations if you’re concerned about age
– In cases where infertility has lasted for more than 6 months and the age of the female partner is more than 35, the couple should consult a fertility specialist for a comprehensive fertility evaluation.
– In cases where infertility has lasted for more than 12 months and the age of the male partner is more than 40, you should consider a sperm DNA fragmentation test.