Why does Rose agree to switch babies with Helen in the novel, The Two-Family House?

Rose is an unhappy woman who feels that Mort is constantly judging her. She believes that she can never measure up to his standards, and she fears that he will never forgive him if she produces yet another girl after having three daughters. Rose is the first of the sisters-in-law to announce that she has given birth to a son and that Helen has given birth to a daughter. She believes this lie will make her happy and will make her life better, but she discovers that is not the case.