Britannica
Sources used in this answer
Why does female fertility decline during the mid-30s?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
infertility
Major structures and hormones involved in the initiation of pregnancy. Also seen, at right, is the development of an egg cell (ovum) from follicle to embryo.
Female fertility begins to decline in a woman's mid-30s primarily due to two age-related physiological changes: a decrease in overall ovarian function and a reduction in the ovaries' reserve of eggs.1
This decline is characterized by several factors:
- Egg Quality: As women age, there is an increased risk of chromosomal abnormalities in the fetus, such as Down syndrome. Even when fertilization occurs, the resulting embryo has a lower probability of successful implantation, which is largely attributed to the diminished quality of the egg rather than issues with the uterine environment.1
- Hormonal Markers: The process is often monitored through follicle-stimulating hormone (FSH) levels, which regulate egg development.1
- Pregnancy Outcomes: Older women experience a higher incidence of miscarriages.1
While natural fertility decreases, successful pregnancies have been achieved by older women using in vitro fertilization with donor eggs from younger women, further suggesting that the primary barrier is the quality and quantity of the individual's own eggs.1