A recent study took into account data gathered in 2006 from almost 1,000 heterosexual couples and found that men and women who equally split child care responsibilities reported far better sex lives. They were happier, too. And when the duties were not evenly split—say the wife took on most of the responsibility—neither was happy. Though the study did not delve into the “why,” the authors conjectured that the husband was unhappy not spending that time with his children, or he was unhappy seeing his wife unhappy.

Source: Parents with Better Sex Lives Share Child Raising Responsibilities