The biggest issue in conception is the age of the mother [1]. As couples don't attempt pregnancy until later (often their mid 30s) this effect is masked as part

The biggest issue in conception is the age of the mother [1]. As couples don't attempt pregnancy until later (often their mid 30s) this effect is masked as partner incompatibility. [1] https://en.wikipedia.org/wiki/Age_and_female_fertility https://en.wikipedia.org/wiki/Age_and_female_fertility