When you went on maternity leave? Did you have to have a medical certificate to do so?

I was originally planning on working until 38 weeks but I am already starting to feel uncomfortable and will definitely not last another 12 weeks at work so thought I may leave around the 34 week mark.

I have 8 weeks sick leave and was wondering if this could be used before using my annual leave and starting maternity payments?

Any help would be appreciated!