Billie, a newspaper film critic, just went through an ugly breakup with her boss, who still wishes to mend their relationship. After a fling with a much younger guy, Billie ends up pregnant and decides that she really wants to keep the baby - and the guy she hooked up with.
As Billie looks through Zack's things, she finds an unfinished note intended for her. She attempts to discover what Zack is keeping from her.
Billie's pregnancy begins to make her more attractive and Zack takes notice of her new curves. However, when Billie has an incident involving self-tanning lotion, Zack is turned off by her appearance.
Billie and Zack agree to see other people. However, this proves to be easier said than done when Billie's pregnancy gets in the way of both of their potential dates.
Billie starts giving dating advices to Zack and Davis, but things go south when the boys' true intentions are uncovered.
Zack's plan to surprise Billie with a newly-installed low flow toilet leads to an unpleasant outcome as he and Billie get into their first major squabble.
Billie requests Abby and Nick to be Godparents, but unintentionally, it causes them to break up. However, Billie has to stop Abby before she does something she will regret when a night with Davis on the town goes too far.
When Billie begins seeing another man, Zack starts to show his jealous tendencies.
After James hires a new film critic to the paper, Billie feels that she has been threatened, and decides to show James how useful she really is.
Billie and Zack begin taking instructional parenting classes, but separately due to their busy schedules. However, Billie decides to go with Olivia and Abby, but when Abby starts to outshine Billie at all the tasks, the course turns into a competition.
Billie tries to cover up the fact that Zack is living with her from her parents, while also worrying that she'll ruin Christmas, just like she has in the previous years. Meanwhile, Nick (Abby's husband) attempts to impress their father.
To prevent the surprise shower they are planning of being exposed, Abby and Nick convince their significant others to spend time with Billie and Zack, but the plan doesn't go as expected when both Billie and Zack dislike their new friends.
While working on an article with Sully, Billie comes across some shocking news about the newspaper. Meanwhile, Zack and Davis decide to go into the sandwich business.
Billie, trying not to nag Zack, tries to trick him into doing chores around the apartment. However, her plan goes awry when Zack takes it upon himself to decorate the nursery. Meanwhile, Davis gets a job at a gay bar in order to earn some extra cash.
Billie invites herself to Zack's high school reunion, but with regrets when she becomes unsure if she can't compete with Zack's hot ex-girlfriend in her pregnant state. Meanwhile, Abby makes a miracle youth juice that she tries to sell at a party that she and Olivia host.
Zack is upset when Billie hires a baby nurse without consulting him. Meanwhile, Davis and Ryan are faced with a difficult choice when they learn surprising news about the nurse.
In the first part of a two-parter, Billie acts as if she gets into labor in order to save Zack from a traffic ticket of speeding. Meanwhile, Olivia and Davis spend the day shopping for a baby gift.
After faking labor pains to get Zack out of a speeding ticket, Billie goes into labor - for real. Unfortunately, things take a turn when Zack gets busted by the officer they had initially lied to and is hauled off to the police station.