cultural string tied around a babies waste - how do we address this with parents

Dear Jacky,

This is certainly a challenging conversation to have with families as we know of the potential physical risks that loose strings / jewellery can pose to babies and children.  There is however, a spiritual and cultural risk to the child and family here if we remove the string entirely.
Having an honest conversation acknowledging their request and reasoning for use is important in the first instance, but it is also important that you clearly inform them of your concerns. 
At the very least, the string must be removed for sleep and rest time to keep the baby as safe as possible during that period of the day.
Having a written request from the parents stipulating their request and awareness of the safety risk together with a co-signed document of mutual agreeance of next steps would be useful to keep on record.
Good luck!
Jane