Orwell's 1984 and Atwood's The Handmaid's Tale share a great deal in common thematically since they are both dystopian novels.
Both novels explore sexual repression. In 1984, the Party insists upon sex as a means of procreation rather than as a source of pleasure or bonding. As a result, Winston and Julia's affair becomes subversive, since they are unmarried and indulging in sex for pleasure alone. The Handmaid's Tale also explores these ideas but from a second-wave feminist standpoint. Gilead proclaims sex is for procreation alone, hence the use of handmaids as baby-making vessels. The scene where the Commander tries impregnating Offred is a prime example of this ethos, with Offred feeling no pleasure from this act. As in Orwell's novel, pleasurable sex becomes subversive, with the male Gilead elite visiting brothels or the Commander trying to initiate an affair with Offred outside of their procreative duties.
Both novels also warn readers about totalitarian regimes. Oceania and Gilead keep their populations firmly under control through propaganda, mass surveillance, and force. While they represent different sides of the spectrum (Oceania is communist, while Gilead's culture is born from fundamentalist Christianity), both are oppressive in the extreme. Winston and Offred become unlikely rebels, initially unwilling to challenge these systems outright before their actions lead them into further subversiveness.