Urban Parents, Particularly Those Who Are Unmarried, Frequently Have Children by Multiple Partners

John Thomas

First published online:

More than a third of urban parents have children by multiple partners, and unmarried parents are more likely to report such multipartnered fertility than are married parents, according to an analysis of data from the Fragile Families and Child Wellbeing Study.1 Overall, a quarter of mothers have children with several partners: Of these, 84% have children by two fathers and 15% have children by three fathers. Black parents are more likely than parents of other racial or ethnic groups to have children by more than one partner. Mothers who have their first child before age 18, have a higher number of births, have a partner of different ethnicity or have worked in the last year have elevated odds of multipartnered fertility. Fathers who are U.S.-born, are in fair or poor health, or have been incarcerated also have elevated odds of such fertility.

In the United States, major changes in marriage and fertility patterns occurred in the latter half of the 20th century, including an increase in the proportion of births occurring outside of marriage (from 4% in 1940 to 36% in 2004). As multipartnered fertility becomes more common, the children from such relationships may receive less emotional and financial support. To date, little research has been conducted on childbearing with multiple partners. This study assessed the prevalence of such fertility among urban parents, and examined individual and relationship factors that might be associated with this phenomenon.

The Fragile Families and Child Wellbeing Study is a national longitudinal study being conducted in 20 U.S. cities with populations exceeding 200,000. It follows a cohort of more than 3,700 children born to unmarried parents and a comparison group of nearly 1,200 children born to married parents over the period 1998–2000. After weighting, the sample is representative of nonmarital births, and nearly representative of marital births, in large American cities. The analyses of the prevalence and correlates of multipartnered fertility are based on data from 4,300 couples interviewed at the birth of their child and again one year later. Information was collected on parents' demographic and socioeconomic characteristics, as well as several psychosocial measures—frequency of church attendance, whether the father had ever been incarcerated and whether either had thought about having an abortion.

Overall, 39% of mothers were white, 31% Hispanic, 22% black and 8% members of other racial or ethnic groups; nearly a fourth of both mothers and fathers were foreign-born, and about a fourth had not completed high school. Twenty-two percent of mothers had had their first child by age 18, 16% at ages 19–20, 43% at 21–29 and 19% at older ages. Five percent of fathers were 19 or younger at the focal child's birth, 44% were in their 20s and 51% were 30 or older. More than half of mothers and fathers had lived with both biological parents at age 15 (54–61%).

Among the 4,209 mothers for whom detailed fertility information was available, three-fourths had had all their children by the same father. Of the remaining mothers, 84% had had children by two fathers, 15% by three fathers and 2% by four or more fathers. The proportion of mothers with children by multiple fathers increased as parity rose: 24% of those with two births, 48% of those with three, 47% of those with four and 72% of those with five or more. In 36% of all couples, one or both parents had had a child with another partner. The proportions of married and unmarried couples reporting multipartnered fertility were dramatically different: 59% of unmarried couples and 21% of married couples.

Multivariate logistic regression analysis found that a number of individual and relationship characteristics were associated with the likelihood of multipartnered fertility. For mothers, age at first birth and parity were significant factors: Women who had had their first child at ages 14–16 or 17–18 had an elevated likelihood of having had children by multiple partners compared with those who did so at 30 or older (odds ratios, 6.0 and 2.3, respectively), and each additional birth more than tripled the odds (3.5). Furthermore, mothers 21 or older at the follow-up interview were more likely than younger women to have had children with multiple partners (4.7). However, mothers who had lived with both biological parents at age 15 had lower odds of multipartnered fertility than those who had not (0.8), and white and Hispanic mothers had lower odds than black mothers (0.6–0.7). Women who attended church more often had lower odds than women who went less frequently (0.9). Other factors associated with an increased likelihood of such fertility were having a partner of different ethnicity (1.4), having worked in the last year (1.3) and having thought about getting an abortion (1.2). Unmarried mothers were also at increased risk of having children by multiple fathers (4.0–5.6, depending on type of relationship).

Fathers aged 19 or younger, 20–24 or 25–29 at the focal child's birth had a decreased likelihood of having had children with multiple partners compared with fathers who were 30 or older (odds ratios, 0.1–0.5). Other factors associated with reduced odds were having lived with both parents at age 15 (0.8), being white or Hispanic (0.4–0.6), being an immigrant (0.7) and having a college education (0.3). Men who were in fair or poor health, had ever been incarcerated or had thought about their partner's terminating her pregnancy by abortion had elevated odds of multipartnered fertility (1.4–2.2). Like their female counterparts, unmarried men had elevated odds of having had children by multiple partners (2.4–4.7).

The researchers point out several limitations of the data set, including a lack of detailed fertility history and the use of slightly different measures for the multipartnered fertility of mothers and fathers. A related weakness is that fathers' fertility was based on reports from their partners, who may underestimate the existence of children by other women.

The researchers believe that current government initiatives promoting marriage for low-income couples will be complicated by the fact that many new marriages will not create "traditional" nuclear families. Instead, many parents will be rearing children across several households, likely diminishing the resources of parental time and money that children receive. As longitudinal data from the Fragile Families study become available, the researchers plan to examine multipartnered fertility prospectively in an effort "to better understand the underlying causal processes, as well as the consequences for parenting, relationship stability, and children's well-being."—J. Thomas


1. Carlson MJ and Furstenberg FF, Jr., The prevalence and correlates of multipartnered fertility among urban U.S. parents, Journal of Marriage and Family, 2006, 68(3):718–732.