Every woman is born with her full supply of eggs — they form before birth, during fetal development, and no new eggs are made afterward. At birth, the ovaries hold roughly 1–2 million eggs; by puberty that's down to 300,000–400,000; and only 400–500 will ever be ovulated across a lifetime. This natural, ongoing decline in number (and, with it, quality) is called ovarian ageing. "Ovarian reserve" is the term for how many eggs remain at any given point. It's assessed with an AMH blood test, a day-2/3 FSH level, and an antral follicle count — an ultrasound that counts the small resting follicles visible at the start of a cycle.
Beyond age, ovarian ageing can be sped up by hormonal imbalance, medical conditions like PCOS or thyroid disorders, and lifestyle factors such as stress, smoking, and poor nutrition.
What "low reserve" changes
A lower reserve mainly affects time and treatment response: fewer eggs are likely to be retrieved in an IVF cycle, and waiting carries more cost than it would at a higher reserve. It does not automatically mean poor egg quality — age is the stronger driver of quality — and women with low reserve do conceive, both naturally and with treatment.
What follows a low result
Usually a franker conversation about timelines: moving to effective treatment sooner, adjusting IVF protocols to the expected response, or considering fertility preservation if pregnancy is planned for later.
When to see a gynaecologist
Worth a visit if you're planning pregnancy and want fertility guidance, have been trying to conceive for 6–12 months without success, or have a history of hormonal or menstrual irregularities.