Keep In Mind: It may take several weeks for mail to stop coming. It's important to get ahead of this by calling/emailing/unsubscribing as soon as possible. If you had pre-term labor (like me), they might still send you things around your baby's due date so don't be caught off guard.
Friends & Family: Offer to do this on behalf of the bereaved if tackling this list is too uncomfortable for them.
Trigger Warnings on Movies, TV Shows, Books, & More - Check out Does The Dog Die, where you can create an account and select numerous triggers where you can check a movie or show before you watch it to see if it has triggers like baby loss, hospitals, or pregnancy.
Mail - If you're comfortable, you can ask your neighbors to screen your mail for you if something could be too triggering. It's a wonderful way they can be helpful to you. Keep in mind that birth and death certificates usually arrive in the mail, so watching for them is important but also quite triggering.
Email - You can have a close friend or family member gain access to your email to have them sort through it. You can also set up some email rules for "baby", "hospital", "newborn", "nursery", or anything other keyword and have it dump into a folder for when you are ready to go through it.
Gerber Grow-Up Plan - call 1-855-459-4435 and ask to be removed from the mailing list because your child died. You will need to provide the full name and address (this is what is normally on the piece of mail). When I did this for myself the gentleman on the line was extremely understanding and kind.
Enfamil - You can call 1-800-BABY123 or email them using the Contact form on their website. I used the General Information subject option and wrote a little note explaining the difficulty and reason to have my removed from all marketing. They responded within 24 hours and were very kind.
Globe Life (Children's Life Insurance) - call 1-866-571-2213, option 1, ask for Customer Service, and ask to be removed from the mailing list because your child died. There was a wait time. Alternative is to email cs@globelifeinsurance.com.
Unsolicited calls - Change your voicemail and explain that you are unable to take the call. They can leave a message or offer the option to send a quick text and you'll get back to them when you can. You can direct all calls directly to voicemail on your phone usually, so this will filter out any spam or unwanted business calls while you are grieving or working.
This list is constantly growing and changing. If you have any tips or ideas feel free to reach out and I will happily add them to this list.