define "Antenatal care contact":
  ["Encounter": type in BCx."Antenatal care contact"]

define "First antenatal care contact":
  BaseData."Antenatal care contact" C
    where C.reasonCode in Cx."First Antenatal Care Contact Choices"

/*
  @dataElement: ANC.B6.DE17 Gestational age
  @activity: ANC.B6 Profile
  @description: Gestational age in weeks and/or days depending on the source of gestational age
*/
define "Gestational age":
  WC.MostRecent(
  [Observation: Cx."Gestational age"] O
    where O.status in { 'final', 'amended', 'corrected' }
      and Coalesce(WC.ModifierExtension(O, 'who-notDone').value, false) is false
      and Last(Split(O.encounter.reference, '/')) = Last(Split(encounter, '/'))
  ).value as FHIR.Quantity

/*
Numerator: Number of pregnant women who had their first ANC contact before 12 weeks (facility level)
Numerator Computation: Count of women whose gestational age <= 12 weeks at the time of first contact
*/
define Numerator:
  exists (
    "First antenatal care contact" C
      where C.period starts during "Measurement Period"
        and ContactData."Gestational age" <= 12 weeks
  )

/*
By Patient Age as of the start of the Measurement Period
Age (10-14, 15-19, 20+)
*/
define "By Age":
  case
    when AgeInYearsAt(start of "Measurement Period") in Interval[10, 14] then "P10Y--P14Y"
    when AgeInYearsAt(start of "Measurement Period") in Interval[15, 19] then "P15Y--P19Y"
    when AgeInYearsAt(start of "Measurement Period") >= 20 then "P20Y--P9999Y"
    else null
  end

/*
Disaggregation: Age (10-14, 15-19, 20+)
*/
define "Age Stratifier":
  Stratifiers."By Age"

/*
Denominator: Total number of antenatal clients with a first contact
Denominator Computation: Count of all women who had first contact within the last reporting period
*/
define Denominator:
  exists (
    "First antenatal care contact" C
      where C.period starts during "Measurement Period"
  )

/*
By Patient Education Level (none, don't know, primary, secondary, higher)
*/
define "By Education Level":
  Patient.extension E
    where E.url = 'http://example.org/guides/who/anc-cds/StructureDefinition/educationlevel'
    return E.value as CodeableConcept

/*
Disaggregation: Education Level (none, don't know, primary, secondary, higher)
*/
define "Education Level Stratifier":
  Stratifiers."By Education Level"

/*
define "Pregnant":
  "Pregnancy" is not null
    or "Pregnancy status" in BCx."Pregnancy status - pregnant"

define "Pregnancy status":
  FHIRHelpers.ToConcept(
    Last(
      [Observation: BCx."Pregnancy status"] O
        where O.status = 'final'
        sort by FHIRHelpers.ToDateTime(effective as FHIR.dateTime)
    ).value
  )
*/
define "Antenatal care case":
  ["EpisodeOfCare": type in BCx."Antenatal care case"]

/*
Initial population: Antenatal clients
*/
define "Initial Population":
  exists (BaseData."Antenatal care case")