The ticking biological clock;which is the best decade?

Women should plan pregnancies when chances of conception are highest, they are in good health, and are more likely to deliver a healthy baby. The optimal biological decade for conception is between 25 to 35 years.

This optimal conception decade is dictated by the fact that women are born with a finite, genetically determined number of eggs in their ovaries. The pool of eggs is highest at birth amounting to about 2 million. However most of these eggs are destined to die, and by puberty, there are only about 500,000 left. The majority of these remaining eggs are also lost with every menstrual period, and only about 400 to 500 are potentially available for conception between puberty and menopause.

In teenage and adolescence, there is physiological immaturity of the reproductive system, hence this is not the optimal period for childbearing. There are more pregnancy associated complications in this age group. Additionally most women are unlikely to have adequate resources to care for a family.

The age of 25 – 35 years is optimal in several respects. There are more eggs available and of good quality, translating into less risk of miscarriages and birth defects. The chances of conception are higher, and remain more or less constant. This is a period of general good health; with less risk of chronic diseases. Once pregnancy occurs, it is more likely to be uncomplicated.

After the age of 35, chances of conception start to decline steeply. The body is unable to replenish the declining pool of eggs. Hence the number of potentially available eggs is much lower, and this is compounded by a decline in the quality of the eggs. Ovulation also becomes more irregular. All these factors reduce the chances of conception. By the age of 40, the chances of conception and live birth have declined by about 50% compared to 30 years of age. If conception does occur, there is a higher risk of miscarriages, birth defects and pregnancy related complications.

Careers and other priorities do not always conform to biological clocks. So what should couples do if they are not ready for a family when it’s biologically optimal? Being aware of fertility decline with age is critical. Women can always take their chances, and hope that they will conceive when ready. Fertility preservation options are available, but at great medical intervention and expense. Eggs can be removed from the ovaries and frozen for future use. Better still, such eggs can be fertilized with sperms then frozen as embryos, which have better survival. These can then be used in the future.

Male fertility mirrors the same decline as in women. Sperm numbers may remain relatively good, but the quality declines with age. Hence the same advice applies.