My best suggestion is to call them before you have baby. Your aama can tell consular that my daughter is having baby and I need to be there to help her morally and physically. I can think of following documents: 1. Your request letter to consular to grant visitor visa for your aama. If this is your first child, then you can say, I need my aama in this moment etc... 2. sponsor letter to aama if you are paying for her expenses here, otherwise just invitation letter but your aama needs to show fund of her own claiming that she has enough fund to stay here for 6 months. 3. request to consular for visitor visa from your aama stating why she wants to visit US and who'll pay for expenses, tickets etc. 4. Your (or your husband's) Bank Statement if you are paying for her expense (or parents can show bank statement) 5. Copy of all the passport pages that are filled out. 6. I-20 7. Transcripts (unofficial should work but if you can get official sealed, that may be better) 8. Dr.'s letter 9. Nepal's property evaluation or other reasons that can show that your aama has obligation to go back to Nepal after visiting US for few months. I think that should be enough. best of luck