I had never heard of a baby ketubah until it was mentioned in my prenatal class.
A baby ketubah or baby naming certificate is a new age tradition. Although not a contract, these certificates are similar to a ketubah in that they are signed by the parents and Rabbi, and are displayed afterwards in your home as a memory of your special event. They typically include the baby's name, Hebrew name, who they were named after, birth stats, and meaningful quote or Torah portion from the week your child was born.
In the pre-COVID era, many parents chose to complement their naming certificate with a matte that friends and family can sign or fingerprint. These days, parents are forgoing that option or simply just filling in the fingerprints themselves.
Even before COVID, when my sister-in-law had twins, she opted to keep the fingerprinting to just family and turned it into a fun activity with her husband and 4-year-old daughter.
Baby ketubahs are a special way to commemorate a new baby and serve as a beautiful piece of art in your nursery.