Having a large family could be in the genes, scientists believe, after finding that men with higher sperm quality had ancestors with more children.

Researchers from the University of Utah in the US discovered an intriguing relationship between the quantity of healthy moving sperm and the number of offspring his forebears going back up to nine generations.

For each additional child in a family, the descendent’s sperm count increased by 1.8 million.

It suggests that coming from a long line of large families could be an indicator of better sperm, and that problems in conceiving are also inherited, even though that may seem impossible.

In a paper presented today (MON) at the American Society for Reproductive Medicine’s (ASRM) annual meeting in Philadelphia, the report authors concluded: “Genetic heritability of male factor infertility may contribute to intergenerational variations in family size.

“This is one of the first studies examining the relationship between intergenerational family size and sperm count as a marker of male factor infertility.

“We found a significant association between sperm count as markers of male factor infertility and family size, suggesting that lower sperm count is related to smaller intergenerational family size.”