solid food

Hello, asianparents! :-) My LO's a premie. She will be turning 7 month-old (corrected age: 5months) on the first week of June. She can now roll over but can't crawl yet. Also, she can't sit by herself. I would like to introduce her solid food already but I've learned that one sign that she's ready for it is if she can sit without support. Do I really have to wait for the time that she can sit by herself before I give her solid food? What was your experience when you intoduce solid foods to your premie baby? Thanks!