Maternity allowance for self employed

Hi ladies, I was wondering if someone could help if they've been in a similar situation. I'm self employed and in order to recieve the full maternity allowance I need to have paid at least 13 weeks of national 2 insurance. I owe about £160 national 2 insurance, if I paid this in 1 lump sum would that count towards the 13 weeks? Or would I literally need to pay weekly? Really appreciate any help or advice you can give me. Thank you x