{
  "resourceType": "Questionnaire",
  "status": "active",
  "item": [
    {
      "linkId": "preg",
      "text": "Pregnancy Dating",
      "type": "group",
      "item": [
        {
          "linkId": "preg-lmp",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "8665-2"
            }
          ],
          "text": "First day of last menstrual period",
          "type": "date"
        },
        {
          "linkId": "preg-visit",
          "text": "Visit date",
          "type": "date"
        },
        {
          "linkId": "preg-edd",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "11778-8"
            }
          ],
          "text": "Expected delivery date",
          "type": "date",
          "readOnly": true,
          "extension": [
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression",
              "valueExpression": {
                "language": "text/fhirpath",
                "expression": "((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate) + 280 days)"
              }
            }
          ]
        },
        {
          "linkId": "preg-ga",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "11884-4"
            }
          ],
          "text": "Gestational age (completed weeks)",
          "type": "integer",
          "readOnly": true,
          "extension": [
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression",
              "valueExpression": {
                "language": "text/fhirpath",
                "expression": "(((365 * (((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(0,4).toInteger()) - iif(((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(5,2).toInteger()) <= 2, 1, 0)) + ((((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(0,4).toInteger()) - iif(((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(5,2).toInteger()) <= 2, 1, 0)) div 4) - ((((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(0,4).toInteger()) - iif(((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(5,2).toInteger()) <= 2, 1, 0)) div 100) + ((((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(0,4).toInteger()) - iif(((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(5,2).toInteger()) <= 2, 1, 0)) div 400) + ((153 * ((((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(5,2).toInteger()) + 9) mod 12) + 2) div 5) + ((%resource.item.where(linkId='preg').item.where(linkId='preg-visit').answer.valueDate).toString().substring(8,2).toInteger())) - (365 * (((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(0,4).toInteger()) - iif(((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(5,2).toInteger()) <= 2, 1, 0)) + ((((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(0,4).toInteger()) - iif(((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(5,2).toInteger()) <= 2, 1, 0)) div 4) - ((((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(0,4).toInteger()) - iif(((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(5,2).toInteger()) <= 2, 1, 0)) div 100) + ((((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(0,4).toInteger()) - iif(((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(5,2).toInteger()) <= 2, 1, 0)) div 400) + ((153 * ((((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(5,2).toInteger()) + 9) mod 12) + 2) div 5) + ((%resource.item.where(linkId='preg').item.where(linkId='preg-lmp').answer.valueDate).toString().substring(8,2).toInteger()))) div 7).where($this >= 0)"
              }
            }
          ]
        }
      ]
    }
  ]
}