Getting custom fields in PrivateMembersData query

I’ve added some custom fields to my members and am querying it in the backend with the code below, but the result does not include the custom fields. What am I doing wrong?

return wixData.query("Members/PrivateMembersData") 
    .then((members) => { 
    // etc

It’s OK, I think I’ve solved it. It looks like once I’ve got the member’s contactID after querying PrivateMembersData by loginEmail I then need to use the wix-crm-backend to get the full details.