http://hl7.org/fhir/StructureDefinition/patient-mothersMaidenName|5.2.0

Mother's maiden (unmarried) name, commonly collected to help verify patient identity.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/string