Recent college graduate and aspiring writer Jefferson "Jake" Briggs (Kevin Bacon) is nervously awaiting his wedding to Kristen "Kristy" Bainbridge (Elizabeth McGovern), sitting in front of the church surrounded by family and friends. His best friend Davis McDonald (Alec Baldwin) reassures him that he has loved Kristy since he was just sixteen, helping to calm his nerves. With love in the air, Jake marries Kristy, stepping into a new chapter of life.
After a brief honeymoon, the duo relocates to New Mexico where Jake aims to pursue graduate school. However, frustrations with his academic program start to mount. Despite Kristy’s encouragement to stick it out, Jake ultimately decides to drop out, leading them back to their hometown in Illinois. Here, Jake grapples with his future prospects, which are complicated when Kristy's father Russ (William Windom) criticizes Jake for not being able to provide for his family.
Jake’s fortunes begin to change when he applies for a position at a Chicago advertising agency. During the interview process, despite his interviewers, Howard (Paul Gleason) and Bill (related to Dennis Dugan), uncovering some discrepancies on his resume, they are captivated by his creativity and ultimately decide to hire him.
With Jake's new job and Kristy's income combined, they manage to buy a home in the suburbs. Yet, as he adjusts to the demands of adult life, Jake finds himself weighed down by responsibilities, all while continuing to work on his novel. Two years later, Davis shows up from New York City with his model girlfriend Erin (Valeri Breiman). Despite Kristy's protests, Jake invites them to stay, creating tension as Davis attempts to lure Jake away to chase his writing dreams, insisting that his life in suburbia isn't enough.
Kristy's desire to start a family begins to clash with Jake's hesitance toward fatherhood. In secret, she halts her birth control without discussing it with Jake. When Kristy eventually reveals the truth and they start fertility testing, Jake feels conflicted but agrees to try for a baby.
The plot thickens when Davis returns for his father's funeral and is welcomed to stay once more. During heartfelt moments, he confides to Kristy his long-standing love for her, to which she replies firmly that her heart belongs to Jake, leaving no room for ambiguity.
Soon after, Kristy shares the joyful news of her pregnancy. As they prepare for parenthood, Jake remains deeply engrossed in his writing. But when Kristy's labor begins, chaos ensues as complications arise, thrusting Jake into a cycle of fear for both his wife and child. After an arduous delivery, they welcome a healthy baby boy into their lives. Relieved and overjoyed, Jake reads his manuscript, 'She's Having A Baby', to Kristy and their newborn, solidifying their new family dynamic in this poignant slice of life.
