Katie is a 25-year-old single mom of two young children: a preschooler and burgeoning toddler. Living in a small town in rural Pennsylvania, Katie works in child care at a local day care center, where the children of parent employees are permitted to accompany their moms and dads during their working hours. The perk of the job is free child care—an expense that would otherwise be unaffordable for Katie. The downside is that she is with her two children around the clock and while at work, never getting a break from being a mom.

Katie spends her nonworking moments in a flurry of feeding, caring for, and shuffling her children to various doctor and therapy appointments (both of her kids have special needs, particularly her toddler, who has a host of medical issues). The father of the children sporadically and inconsistently asks to spend time with the 4-year-old before disappearing for weeks on end. He isn’t involved with the toddler’s life whatsoever. His financial contribution to the children’s needs is minimal. Katie says she desires a consistent fatherly presence in her children’s lives, longs to share the burdens of parenthood with someone else, and constantly worries about money. She is anxious about her ability to meet her family’s financial necessities and worries about addressing their emotional needs.

Even in her exhausted state—we spoke at 10 p.m., after she finally got both kids to sleep and dinner for herself—Katie’s deep love for her children is evident. So are her concerns about parenting. Much of her daytime energy goes toward caring for other people’s kids—that’s how she pays the bills—and when both of her children vie for her attention at night, she feels torn. “There are two of them and only one of me,” she says.

In Katie’s words, she’s drowning. And in the words of a group of social worker researchers, she’s the head of a “fragile family.”

What are “fragile families”?

In 1998 researchers out of Columbia University and Princeton University embarked on a study of epic proportions: They visited the maternity wards of hospitals in 20 U.S. cities to interview the parents of nearly 5,000 newborn babies, with an oversampling of unmarried parents and their children. Because of their higher risk of poverty and family dissolution than traditional families, one of the study’s founders, Ron Mincy, termed this group of unmarried parents and their children “fragile families.” The study—which has gone on to follow the large study sample through the present day—is known today as the Fragile Families and Child Wellbeing Study (FFCWS).