<StructureDefinition xmlns="http://hl7.org/fhir">
  <id value="first-menstrual-period-observation" />
  <url value="https://simplifier.net/guide/hmb-fhir-ig/StructureDefinition/first-menstrual-period-observation" />
  <name value="FirstMenstrualPeriod" />
  <title value="First Menstrual Period Observation" />
  <status value="draft" />
  <description value="First menstrual period." />
  <fhirVersion value="4.0.1" />
  <kind value="resource" />
  <abstract value="false" />
  <type value="Observation" />
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Observation" />
  <derivation value="constraint" />
  <differential>
    <element id="Observation.status">
      <path value="Observation.status" />
      <patternCode value="final" />
      <mustSupport value="true" />
    </element>
    <element id="Observation.category">
      <path value="Observation.category" />
      <slicing>
        <discriminator>
          <type value="value" />
          <path value="coding" />
        </discriminator>
        <rules value="open" />
      </slicing>
      <min value="1" />
      <max value="1" />
    </element>
    <element id="Observation.category:obstetrics">
      <path value="Observation.category" />
      <sliceName value="obstetrics" />
      <min value="1" />
      <max value="1" />
    </element>
    <element id="Observation.category:obstetrics.coding">
      <path value="Observation.category.coding" />
      <min value="1" />
      <max value="1" />
    </element>
    <element id="Observation.category:obstetrics.coding.system">
      <path value="Observation.category.coding.system" />
      <fixedUri value="http://terminology.hl7.org/CodeSystem/observation-category" />
    </element>
    <element id="Observation.category:obstetrics.coding.code">
      <path value="Observation.category.coding.code" />
      <patternCode value="social-history" />
    </element>
    <element id="Observation.category:obstetrics.coding.display">
      <path value="Observation.category.coding.display" />
      <patternString value="Social History" />
    </element>
    <element id="Observation.code">
      <path value="Observation.code" />
      <patternCodeableConcept>
        <coding>
          <system value="http://loinc.org" />
          <code value="63888-2" />
          <display value="Age at first menstrual period" />
        </coding>
      </patternCodeableConcept>
      <mustSupport value="true" />
    </element>
    <element id="Observation.subject">
      <path value="Observation.subject" />
      <min value="1" />
      <type>
        <code value="Reference" />
        <targetProfile value="http://hl7.org/fhir/StructureDefinition/Patient" />
      </type>
      <mustSupport value="true" />
    </element>
    <element id="Observation.effective[x]">
      <path value="Observation.effective[x]" />
      <type>
        <code value="dateTime" />
      </type>
      <mustSupport value="true" />
    </element>
    <element id="Observation.value[x]">
      <path value="Observation.value[x]" />
      <type>
        <code value="Quantity" />
      </type>
      <mustSupport value="true" />
    </element>
    <element id="Observation.value[x].unit">
      <path value="Observation.value[x].unit" />
      <patternString value="a" />
    </element>
  </differential>
</StructureDefinition>