As part of a fertility research project, a male scientist agrees to carry a pregnancy in his own body.
Alex Hesse (Arnold Schwarzenegger) and Larry Arbogast (Danny DeVito) are working on a new drug which will reduce the chances of a woman's body rejecting her baby, and thus causing a miscarriage. When their research funding is withdrawn, and human experimentation is denied to them, they decide to test the drug by briefly impregnating Hesse. However, Hesse becomes attached to his unborn baby.—Rob Hartill
Austrian research geneticist Dr. Alex Hesse (Arnold Schwarzenegger) and his OB/GYN colleague Dr. Larry (Danny DeVito) Arbogast invent a fertility drug, "Expectane", designed to reduce the chances of a miscarriage. Alex says that the female body is miscarriage prone due to the body's natural tendency to reject foreign matter. The body mistakes the embryo as unwanted foreign substance and creates antibodies to fight and reject it. Expectane neutralizes the antibodies and leads to successful embryo attachment.The drug has been tested on a chimpanzee, who has had a history of miscarriages and is now 7 months pregnant due to her treatment with Expectane.
Head of the University review board Noah Banes (Frank Langella) informs Larry that the FDA rejected the proposed drug after Alex and Larry's presentation. With the drug unapproved by the FDA, the colleagues are unable to test the drug and cannot continue their research. Banes asks Alex to empty his lab, which he refuses to do. Larry begs Banes that he has invested $300,000 in the development of the drug and asks for some slack.Banes has recruited geneticist Dr. Diana Reddin (Emma Thompson) and her ovum Cryogenics project to the University. Diana will set up her lab where Alex is resident currently. Larry notices that Diana carries an entire selection of frozen eggs for her experiments.Louise (Aida Turturro) is the receptionist at Larry's clinic.
Alex plans to start over in Europe as he has no lab, no funding or any future in the USA. Larry suggests they can still perform the experiment, with Canadian firm Lyndon Pharmaceutical offering to fund them provided they find a volunteer. Alex questions the likelihood of a pregnant woman taking an unapproved drug, but Larry suggests omitting the volunteer's gender. Larry says that Moe the chimp went 5 months pregnant when put on Expectane.Larry convinces Alex to impregnate himself with an ovum code-named "Junior". Larry says that Alex only needs to carry the embryo through the first trimester, which will give their data and then they will terminate the pregnancy. Larry argues that many other scientists have tested their own vaccines and drugs on themselves.Larry promises that he can find an egg, and then proceeds to steal one frozen egg from Diana's Cryogenic container. The egg was labeled "Junior" by Diana. Larry fertilizes the egg using Alex's sperm and injects the egg into Alex's abdomen in the Peritoneal cavity.Larry lies to Alex that the egg belongs to a colleague, who got it through an anonymous harvest.
That night, Alex dreams his potential offspring has his own face. Alex is staying with Larry at his house, during the protocol. The urine test indicates that Alex is pregnant. He is to take Expectane 6 times a day.As weeks go by, he complains to Larry of sore nipples, morning sickness, cramps, chats incessantly about walks, massages, and naps. Diana had shared her lab space with Alex as she felt bad for kicking him out. Alex started bonding with Diana and shared his physical discomfort with her.
Contemplating fatherhood after watching television commercials, Alex breaks down sobbing. Larry visits a maternity convention where Lyndon Pharmaceuticals executives are attending. Larry promises them results within a week, which Banes overhears. Bane suspects that Larry is conducting human experimentation without authorization. Alex and Diana also attend the conference and develop a mutual attraction towards each other.
When the time comes for Alex to end the experiment and release the results to Lyndon Pharmaceutical, he continues taking the drug and decides to carry the pregnancy to term. Larry had told Alex to stop taking Expectane, which would disrupt the embryo and it would be reabsorbed naturally into his body.10 weeks later, Larry notices Alex's growing belly and realizes that he is still pregnant. Initially annoyed, Larry agrees to keep it hidden. Alex develops a romantic relationship with Diana.
Banes finds that Larry and Alex are still buying Expectane components through Diana. Banes confronts Alex and Larry and wants to know if they are coloring outside the lines. Banes goes up to Alex's room and finds a supply of Expectane and deduces that there is a pregnancy in the house. Banes takes a sample and has it tested. The sample has high dosage of estrogen and Progesterone, consistent with someone preparing to undergo a sex change operation. Banes realizes that Alex is pregnant.
Larry takes Diana out to dinner. Diana mentions that she also experimented on herself when she froze her own egg and labeled it Junior. Alex returns home and confronts Larry that he stole the egg from Diana and that it is her own egg.When Angela comes over to Larry's, she sees Larry touching Alex's belly and believes they are gay partners. Alex reveals his pregnancy to Angela (Pamela Reed), who also happens to be pregnant by Aerosmith's personal trainer. Larry is Angela's attending physician as per her request.
Alex meets Diana at her lab and tells her the truth. Diana is stunned and angry when it is revealed that the "Junior" ovum is hers, and Banes attempts to take credit for the experiment. Banes says that the University has a contract with Alex, and any commercial applications of Alex's experiment are the property of the University. Alex manages to escape.Disguised as a woman, Alex hides in a retreat for expectant mothers, blaming his masculine appearance on Anabolic steroid use.Diana visits, telling him it does not matter who is pregnant because he is the father, and she is the mother. Larry reveals the experiment's data to Lyndon Pharmaceutical, who agree to partner with them.
Alex experiences abdominal pain from the start of labor, calling for Larry and Diana. As Diana rushes to the resort, Larry tells a fellow doctor to prepare for an emergency c-section. A hospital staffer overhears and alerts Banes, who summons the media and the University Dean, hoping to take credit for the world's first pregnant man.Warned by a colleague, Larry creates a decoy for Alex to allow a private c-section. When Larry arrives, the news media only see the pregnant Angela, discrediting Banes, who is fired by the Dean.Diana and Alex enter the hospital by the fire escape, and he has an emergency c-section. Sent to keep Angela company in the waiting room, Diana finds her in labor and becomes her delivery coach. Alex gives birth to a healthy baby girl, and Larry announces the arrival to Diana, who is assisting Angela with contractions. Diana leaves Angela with Larry and rushes to see the baby, whom she and Alex name Junior. Larry delivers Angela's child, and they reconcile to raise the boy, Jake, as their own.
One year later, the families all go on vacation together and celebrate the birthdays of Junior and Jake. Diana is pregnant with their second child, and Angela mentions wanting another baby but not wishing to endure pregnancy again; they all try to convince a reluctant Larry to carry the child.
