"We’re in the thick of what one sociologist calls “the changing timetable for adulthood.” Sociologists traditionally define the “transition to adulthood” as marked by five milestones: completing school, leaving home, becoming financially independent, marrying and having a child. In 1960, 77 percent of women and 65 percent of men had, by the time they reached 30, passed all five milestones. Among 30-year-olds in 2000, according to data from the United States Census Bureau, fewer than half of the women and one-third of the men had done so. A Canadian study reported that a typical 30-year-old in 2001 had completed the same number of milestones as a 25-year-old in the early ’70s.
The whole idea of milestones, of course, is something of an anachronism; it implies a lockstep march toward adulthood that is rare these days. Kids don’t shuffle along in unison on the road to maturity. They slouch toward adulthood at an uneven, highly individual pace. Some never achieve all five milestones, including those who are single or childless by choice, or unable to marry even if they wanted to because they’re gay. Others reach the milestones completely out of order, advancing professionally before committing to a monogamous relationship, having children young and marrying later, leaving school to go to work and returning to school long after becoming financially secure."
....Read more of Robin's Marantz Henig's "What Is It About 20-Somethings?" piece here.
My thoughts: The risk for unhealthy babies does get higher into your 30s/40s. It's sort of freaky when the 16 year old single mom's baby is healthier than yours even if your financially/mentally suited.