Plurality is both a characteristic of a pregnancy and a characteristic of a patient (e.g., single, twin, triplet etc. and includes the number of fetuses delivered live or dead at any time in the pregnancy)

The VRCPL has a Plurality Observation profile (http://build.fhir.org/ig/HL7/vr-common-library/branches/master/StructureDefinition-Observation-plurality-vr.html) that has the mother, child, and fetus as subjects.

FHIR Patient only has the ability to record Patient.multipleBirth[x]. This piece of information by itself does not give you enough information about the set – plurality also needs to be captured.

On consultation with the Patient Administration WG at the WGM about the recommended way to represent Plurality for a patient, they pointed us to their new patient-multipleBirthTotal extension (http://hl7.org/fhir/extensions/1.0.0/StructureDefinition-patient-multipleBirthTotal.html) (added in FHIR R5):

• this extension is to be used on the Patient.multipleBirth[x] element
• it is now possible to use R5 extensions in R4 IGs

IG update actions:

• For Plurality as a characteristic of a Patient who is part of a multiple delivery: add the patient-multipleBirthTotal extension to the VRCPL Patient profiles (on Patient.multipleBirth[x])

For Plurality as a characteristic of a pregnancy: update the current Plurality Observation profile (http://build.fhir.org/ig/HL7/vr-common-library/branches/master/StructureDefinition-Observation-plurality-vr.html) to only have the mother as the subject (remove child and fetus subject)