How Age Affects Female Fertility

Women are born with all the eggs they will ever have, typically around one to two million. By puberty, this number has already declined to approximately 300,000 to 400,000. Throughout reproductive life, eggs are lost through both ovulation and natural cell death.

These figures represent averages. Individual variation is substantial, which is why personalised fertility assessment can be valuable.

When discussing age-related fertility decline, two distinct factors are at play: the number of eggs remaining (quantity) and the chromosomal health of those eggs (quality).

Egg quantity can be estimated through an AMH blood test and ultrasound assessment of antral follicles. These tests provide useful information about ovarian reserve.

Egg quality is more challenging to assess. As women age, a higher proportion of eggs carry chromosomal abnormalities. This is why older women experience higher rates of:

• Difficulty conceiving
• Miscarriage
• Chromosomal conditions such as Down syndrome

Importantly, egg quality cannot be determined by blood tests or ultrasound alone. A woman may have excellent ovarian reserve markers yet still have age-related egg quality decline.

One of the most common misconceptions is that regular menstrual cycles indicate good fertility. While regular ovulation is certainly important for conception, it doesn't tell the whole story.

Women typically continue having regular periods well into their 40s, often until just a few years before menopause. However, the eggs released during these cycles are increasingly likely to be chromosomally abnormal.

Key point: Regular periods confirm you're ovulating, but they cannot tell you about the quality of the eggs being released or how many eggs remain.

This is why age remains the most important factor in fertility assessment, regardless of menstrual regularity.

General guidelines suggest seeking advice if you haven't conceived after:

• 12 months of regular unprotected intercourse if under 35
• 6 months if aged 35 to 39
• 3 months if aged 40 or over

However, proactive assessment can be valuable even before you start trying, particularly if you:

• Are considering delaying pregnancy for career or personal reasons
• Have a family history of early menopause
• Have had previous ovarian surgery or cancer treatment
• Simply want to understand your fertility status to inform future planning

A baseline assessment can provide valuable information without committing you to any particular course of action.

Understanding your options helps you make informed decisions at any stage: