Synopsis: In Mother Didn’t Tell Me, Jane Morgan, a young radio jingle writer for a leading Los Angeles advertising agency, has a terrible cough and goes to consult a doctor, William Wright, who turns out to be young, handsome and available. Jane takes a fancy to Bill and, later that same evening, phones him to say she is feeling worse. Bill offers to make a house call and ends up making a dinner date with Jane for later in the week. However, on their way to dinner, Bill has to make a house call, and Jane is forced to wait in the car. After an hour, she goes for a stroll, and when Bill comes back a moment later, he thinks she has already left and drives away.
Later, however, he drops by Jane’s apartment and prepares a dinner, during which Jane tells him that she lost both her parents in an accident about five years earlier. While on their second date, Bill proposes and takes her to meet his mother. Mrs. Wright, a doctor’s widow, tells Jane that she is jumping into marriage too quickly and does not realize what it is like to be married to a doctor. After Mrs. Wright asks Jane if Bill has told her about a woman named Helen, Jane questions Bill. Bill explains that Helen worked in his office as a technician to earn money for medical school and, at Bill’s insistence, plans to become his associate when she finishes her studies.
Despite some apprehensions on Jane’s part, Bill and Jane marry and end up spending their honeymoon in Detroit because Bill wants to attend a medical convention there. On their return to Los Angeles, the newlyweds move into a semi-furnished house that has been provided to them by one of Bill’s grateful patients. While Bill’s friend, Dr. Pete Roberts, and his wife Maggie help them move in, Maggie tells Jane about some of the realities of being a doctor’s wife.
One evening, Bill arrives late for a dinner party, then immediately has to leave. One by one, all the doctors at the party are summoned back to work and their wives are left to talk with one another. Soon after, Jane finds moving men emptying the house, and Bill, who has forgotten to tell Jane that a pregnancy test she took came back positive, explains that the owner needs it back earlier than expected. Bill has, however, made a down payment on another house, without consulting Jane, and it turns out to be run down and lacking furniture. Eventually, the house is fixed up and Jane gives birth to twins, a boy and a girl.
Just before he is to attend a dinner party to celebrate his birthday, Bill receives a cable from Helen, who has finished her studies in the East and is returning that evening on a flight to be his new associate. Jane does not like the idea of Bill working with Helen but asks him to bring Helen to the dinner party after he picks her up at the airport. Maggie brings famous psychiatrist Dr. Bruce Gordon to the party and he immediately begins flirting with Jane and Maggie. When Bill and Helen eventually arrive, they find Jane and Gordon dancing to a pastiche South Seas beat he learned when he studied in Bali.
The meeting between Jane and Helen does not go well, and Jane is distressed to discover that Helen is gorgeous. Later, when Jane again asks Bill not to take Helen on as his associate, they have a fight and Jane ends up sleeping in the children’s room. The next day, Jane calls Bill’s office and leaves a message saying she is not feeling well, hoping that he will rush home. She then puts on an attractive nightgown, hops into bed and awaits her husband. However, Helen comes instead of Bill and more friction develops between them.
Bill returns home to find Jane packing to leave, and she declares she cannot be a doctor’s wife as well as share her husband with another woman. Bill’s mother then arrives and tells Jane that she has handicapped Bill personally and professionally. After Bill arranges for Jane to stay at a remote cabin, he loads up the car and they are about to leave when Jane discovers that the twins have eaten poisonous ant paste. They rush to the hospital, where the children have their stomachs pumped and recover.
Later, Bill tells Jane, who still intends to leave the next day, that Helen is going off to work in Chicago. Bill’s mother then admits to Jane that she persuaded Helen to leave by telling her that she would tell Bill that she and Helen were plotting to break up his marriage. Jane and Mrs. Wright become more friendly, and Jane and Bill reunite.