This is a very common question but not an easy answer. First, the term “quality” is not well defined in reproductive medicine: is it based on appearance of the embryo?; is it the chromosomal competence of the embryo; or the structrual/genetic make-up? The first two metrics are definable – we can grade an embryo base on appearance; we can test the embryo for the chromosomal content. Neither of these qualifiers correlate well with the ability for the embryo to result in a live birth. Structural/genetic make-up is not able to be tested at this time.
Traditionally, we have considered a woman’s age as the dominant forcé contributing to egg “quality.” The percentage of chromosomally abnormal embryos increase as the woman ages. While male fertility declines with age, we do not have as much information on their contributions to embryo quality.
Suggested for you: Embryo Quality & Grading – Does It Affect IVF Success?.