Complex sentence: Mothers with one or more immature daughters in addition to their infants are in contact with their infants less than those with no older immature daughters, because the mothers may pass the parenting responsibilities to her daughters.
Split into simpler sentences: Mothers with one or more immature daughters in addition to their infants are in contact with their infants less than those with no older immature daughters. This is because the mothers may pass the parenting responsibilities to her daughters.