Women who’ve never had children are just as content at midlife as mothers of the same age and in the same circumstances, according to a 2007 study from the University of Florida. Whether a woman gives birth seems less crucial to her well-being than such factors as education, work and earnings, as well as relationships with family and friends. When children make their appearance is key, though. The study found that women who gave birth before the age of 19 were the least happy. —Nancy Bilyeau