Scientists have discovered a genetic variant that may make some parents more likely to have girls than boys. The study, published in the journal Proceedings of the Royal Society B, analyzed the genomes of over 450,000 males and females in the UK. Researchers found one particular version of a gene, named rs144724107, which boosts a person's likelihood of having a daughter by 10%. While it is unclear whether this variant needs to be carried by mom, dad or both to influence offspring sex ratio, the study suggests that this genetic variant could play a role in determining the sex of future offspring.

Source: https://www.livescience.com/health/genetics/parents-who-have-this-gene-may-be-more-likely-to-have-a-girl