During their various moments together, Winston and Julia did not discuss getting married, assuming it was hopeless.
Julia asked about Winston’s wife, Katherine, whom he’d been separated from for a long time. Describing her he used the Newspeak word, Goodthinkful. This meant a person incapable of Anti-Party thought.
He began explaining the discomfort of his marriage but Julia knew all the details. This was because of the fact girls had been so trained.
Julia knew the purpose of the Party’s sexual puritanism. Sexual unfulfillment could produce hysteria which could be used by the Party to create fervent Party support and leader worship.
Parenthood was twisted, so that the children would be turned against their parents, taught to spy on them so the family became an extension of the Thought Police.
Winston perceived that Kathrine, his wife, would have denounced him to the thought police if she was intelligent enough to realise is his unorthodoxy.