If your child is born prematurely you are entitled to take paternity leave providing you would have been working for your employer for 26 weeks by the qualifying week if the pregnancy had gone to full term.
You must normally give your employer notice that you want to take paternity leave in, or before, the 15th week before the week the child is due. But if the child is born prematurely this is not possible, and you must instead give notice as soon as is reasonably practicable for you to do so.