The biolog­ical clock

Chances of pregnancy

A young, healthy couple has about a 25–35% chance of conceiving in each cycle. From the second year of regular unprotected sex, this chance starts to fall, and in women aged 35 to 42 it is about 10–15% per cycle. This happens for the following reasons:

• Fewer eggs. In each cycle, only one egg reaches full maturity. Every woman is born with a reserve of 1 to 2 million eggs. However, this falls steadily until it runs out after about 400 cycles.
• Ageing of the eggs. Eggs age like every other cell in the body. This ageing can cause changes in the chromosomes and end in miscarriage.
  At least half of all miscarriages can be attributed to such chromosomal abnormalities.

This means that older women have fewer eggs, which have also “aged” more. On the one hand this lowers the chance of a pregnancy, and on the other it raises the chance of a miscarriage.

How often miscar­riages happen

At the age of 20–30, the miscarriage rate is about 15%, while in women over 40 it reaches as much as 50%.

Early testing and starting treatment

Women who want to have children should start preventive check-ups early. In this way, possible problems can be diagnosed and the right treatment can be started. Also read about egg freezing and egg donation.

It concerns men too

Men over 50 may have a fall in sperm quality and in testosterone levels, which can also lead to a drop in libido.