The biology of time: why does fertility decline?
Unlike men, women are born with a finite number of eggs that do not replicate during adult life. This ovarian reserve naturally decreases from birth. But the challenge is not only quantity, but also quality.
According to reference studies such as Heffner et al., fertility loss becomes especially critical from an average age of 37. From that point onwards, the probability of pregnancy decreases while the miscarriage rate increases exponentially.