Plot

Two couples with the same surname pursue in-vitro fertilization and wait for their upcoming babies. Trouble ensues when they find that the sperms of each couple have been mixed with each other.

Varun Batra (Akshay Kumar) is the CEO of a Volkswagen showroom in Mumbai. Varun is the best salesperson at his dealership. Deepti Batra / Deepu (Kareena Kapoor Khan) is his spunky wife and is a celebrity journalist. The two are a happily married couple going on seven years. They are trying hard for a kid, but it's not working out.

Deepti is very organized and meticulous. She has marked all the calendar days when she is ovulating and expects Varun to have sex with her. But she is bossy and a tad condescending about it. Varun feels pressured for sex and is unable to perform in bed. Deepti tries to seduce Varun, and he has sex, but later admits that he was just faking an ejaculation. They go for a family function to Delhi and Varun agrees to have sex with Deepti on the flight as he understands how important it is for Deepti, and he knows that they will not be able to do anything among relatives. At the family event, all the aunts come over to Deepti and share their home remedies to conceive a child, which infuriates Deepti.

In Delhi, Varun's sister Richa (Anjana Sukhani) suggests that they visit an IVF specialist Dr Anand Joshi (Adil Hussain) who is supposed to be the best fertility specialist in Mumbai. Anand looks at the reports and concludes that Deepti's egg count is depleting quickly, and so they don't have a lot of time. He adds that Varun's sperm is healthy, but they become inactive when they enter Deepti's uterus. Anand explains that the duo will have to undergo In-Vitro fertilization to conceive a child. Varun has a crush on Anand's wife Dr. Sandhya Joshi (Tisca Chopra). The clinic claims a high success rate and have already delivered 26,119 children to their respective parents. They agree, Varun submits sperm samples, and Dr. Joshi seemingly places the couple's embryo created in his lab in Deepti's uterus.

After the IVF is complete, 12 days later Sandhya calls Deepti in for an emergency check-up. At the clinic the due meet Honey Batra (Diljit Dosanjh) and Monika Batra (Kiara Advani). Anand and Sandhya explain that due to the same surname, the sperm got mixed up. Which means Honey's sperm in Deepti's egg, inside Deepti and Varun's sperm in Monika's egg inside Monika. Honey is a loud, typical Punjabi guy, who charms people with his good nature and likes to show off his wealth with gaudy clothes and fancy cars.

Shocked beyond belief, both couples attack the two doctors. The doctors suggest that the couples go for a minor procedure so there is no chance of pregnancy.

Despite long odds, both ladies get pregnant. Varun wants Deepti to abort. Varun considers Honey to be an imbecile and simply cannot bear the thought of his genes in a child that Deepti would bring up. Varun wants to abort vehemently, but Deepti is not sure.

Varun even tells Honey that he doesn't consider the kid inside Deepti as his own. Honey and Monika are different, they consider both kids as their own (the one inside Monika and the one inside Deepti) To ensure that Deepti and Varun don't abort, they buy an apartment next to Varun and move in.

Honey even suggests that after delivery Deepti hands over her kid to Monika. Deepti is livid at the suggestion, but Varun is cool. Deepti asks Richa to draw up a legal contract that states that after delivery both families won't have any rights over each other's kids. But when they call Monika and Honey for the signing, they bring their own contract stating how their kid inside Deepti should be brought up and his / her career choices. It's clear that Honey and Monika want deeper relations while Deepti and Varun want to exit any possible relations.

Varun and Deepti initially project frustration against Honey and Monika during the first six months of pregnancy for interfering in their lives. However, during a routine check-up in the seventh month of pregnancy, Sandhya advises Deepti to try talking to Monika, who is probably going through as much as she is, being emotionally distressed. Realizing that she needs to try to understand the situation, Deepti asks Monika out for a street food treat, during which they start getting to know each other.

Monika tells Deepti has she had a miscarriage twice before. However, Varun still nurses a negative attitude, especially since Deepti is not carrying his child. She takes a stand in Honey's and Monika's favor for the first time, angrily telling Varun that he never cared to understand anything that happened post the mishap.

Varun, with Deepti's confrontation still fresh in his mind, makes an attempt to bond with Honey when they meet at a bar, and they almost strike a chord with each other, until Honey expresses concern over Deepti's work commitments, which he thinks will have a negative impact on the child. Varun, incensed, snubs Honey in a possessive manner, an argument between the two escalates until Varun storms out and Honey is arrested after the manager drops a call.

That night Monika has pains and asks Varun to help out. He takes her to the hospital. Monika gives birth to a girl, prematurely, but her chances of survival are slim. However, the newborn is shifted to a critical unit in grave condition, having been born with a respiratory defect, accelerated by Monika's history of miscarriages, with little chance of survival. As it dawns on him that the baby is in fact his, Varun begins crying and hugs Honey when he arrives after being let off with a warning.

Varun completely changes 180 degrees. Even as Honey and Monika reunite, he goes home and breaks down in Deepti's arms, apologizing for his past insensitivity. Monika's kid survives and Monika and Honey take her home with great pomp and celebration. Deepti and Varun participate 100% in her recovery. 2 months later, Deepti goes into labor and at the precise moment, Varun gets a slip disc. Honey takes Deepti and Varun to the hospital. Deepti has a baby girl as well.