An increasing number of couples in the United States are entering their first marriage having already had a child together, raising important questions about whether and how these couples' marriages differ from newlywed couples who enter marriage without children. The current study used 5 waves of data collected over the first 4.5 years of marriage from a sample of ethnically diverse, first-married newlywed couples living with low incomes to examine the effects of premarital parenthood on couples' self-reported satisfaction, observed communication, and marital dissolution over time. Among couples who entered marriage with a shared biological child (premarital parents), satisfaction levels were lower and communication was less effective, less positive, and more negative than couples entering marriage without children. Rates of change in marital functioning did not differ between groups, but the rate of marital dissolution was twice as high among premarital parents (19.1%) relative to couples who were not parents at the start of marriage (9.5%). These between-groups differences remained robust after controlling for several demographic differences (race, age, education, household income, work status, relationship length, premarital cohabitation), and initial differences in communication did not account for between-groups differences in marital satisfaction or dissolution. Together, these findings indicate that newlywed marriage unfolds in similar ways for low-income couples with and without children at the start of marriage, but couples raising children at the time of marriage have greater vulnerability to marital distress and dissolution. Further research is needed to characterize this risk and how interventions can offset it. (PsycInfo Database Record (c) 2020 APA, all rights reserved).