Hi mama! From what I know, you can file your maternity benefit claim kahit before your due date, a few of us tried submitting around 7-8 months pregnant pa lang, and yes, they do release it in installments so you get money agad kahit hindi pa fully due. The best thing to do is go directly to your nearest SSS branch in January with your maternity notification form, valid ID, and proof of contributions, they're really helpful dun and pwedeng sagutin nila lahat ng specific questions mo about the current process kasi mabilis mag-update ang requirements. Good luck, mama!