From day 14 onward, simplify. Take out tall shelves and hammocks that a newborn could fall from, and drop the cage down to one level if you can. Solid floors only. Bar spacing that a soupling could slip through needs covering with fine mesh or fleece. Give her nesting material she can shred: plain kitchen roll, unscented tissue, strips of fleece. Do not give string, cotton wool nesting fluff, or anything with long fibres that can wrap around tiny limbs. Increase her protein a little. Cooked egg, plain cooked chicken and a good quality block are all easy wins. Fresh water she can reach without climbing. House the father separately before the birth. Rats can conceive again within hours of giving birth, so back to back litters are a real risk. Once she is nesting, stop deep cleaning. Spot clean only, and leave the nest alone entirely for the first few days.