Warning! Contains spoilers for The Handmaid's Tale season 5!Serena and Fred Waterford had a miracle baby in The Handmaid's Tale — but was Fred really the father and, if so, when was Serena's baby conceived? The couple were in different cells and as estranged from one another as they've ever been, but a moment of reconciliation in The Handmaid's Tale season 3 could be the answer. The Waterfords were previously believed to both be infertile. Fred had failed to get both June and a previous handmaid pregnant, despite many attempts even outside Gilead's "ceremony". Serena was shot in her lower abdomen by a protester in the days before Gilead, and her injuries damaged her reproductive organs. Yet in The Handmaid's Tale season 4, episode 2, "Nightshade," Serena gets some shocking news: blood tests carried out in Canada show that she's pregnant, kick-starting the Serena's baby Handmaid's Tale plot arc.

https://screenrant.com/handmaids-tale-serena-pregnancy-when-fred-father/