Silly question UK ladies

Alicia
Silly question, (UK ladies, only because it's legal related but other places can comment if they have an insight) I'm TTC I'm also getting married in 20 months. If I was to have my baby before my wedding I'd have to put my maiden name on the birth cerficate. Would I be able to change it to my married name after or would it have to stay as my maiden name? Can anyone tell this process if you have been through it.