diff --git a/components/settings/index.js b/components/settings/index.js
index bfddbc7..b91acbc 100644
--- a/components/settings/index.js
+++ b/components/settings/index.js
@@ -13,6 +13,7 @@ import TempSlider from './temp-slider'
 import openImportDialogAndImport from './import-dialog'
 import openShareDialogAndExport from './export-dialog'
 import PasswordSetting from './password'
+import UseCervixSetting from './use-cervix'
 
 export default class Settings extends Component {
   constructor(props) {
@@ -24,6 +25,7 @@ export default class Settings extends Component {
     return (
       <ScrollView>
         <TempReminderPicker/>
+        <UseCervixSetting/>
         <View style={styles.settingsSegment}>
           <AppText style={styles.settingsSegmentTitle}>
             {labels.tempScale.segmentTitle}
diff --git a/components/settings/use-cervix.js b/components/settings/use-cervix.js
new file mode 100644
index 0000000..668a0e8
--- /dev/null
+++ b/components/settings/use-cervix.js
@@ -0,0 +1,48 @@
+import React, { Component } from 'react'
+import {
+  View,
+  TouchableOpacity,
+  Switch
+} from 'react-native'
+import AppText from '../app-text'
+import {
+  useCervixObservable,
+  saveUseCervix
+} from '../../local-storage'
+import styles from '../../styles/index'
+import { settings as labels } from '../../i18n/en/settings'
+
+export default class UseCervixSetting extends Component {
+  constructor() {
+    super()
+    this.state = {useCervix: useCervixObservable.value}
+  }
+
+  render() {
+    return (
+      <TouchableOpacity
+        style={styles.settingsSegment}
+      >
+        <AppText style={styles.settingsSegmentTitle}>
+          {labels.useCervix.title}
+        </AppText>
+        <View style={{ flexDirection: 'row', alignItems: 'center' }}>
+          <View style={{ flex: 1 }}>
+            {this.state.useCervix ?
+              <AppText>{labels.useCervix.cervixModeOn}</AppText>
+              :
+              <AppText>{labels.useCervix.cervixModeOff}</AppText>
+            }
+          </View>
+          <Switch
+            value={this.state.useCervix}
+            onValueChange={bool => {
+              this.setState({ useCervix: bool })
+              saveUseCervix(bool)
+            }}
+          />
+        </View>
+      </TouchableOpacity>
+    )
+  }
+}
diff --git a/i18n/en/settings.js b/i18n/en/settings.js
index 7b23f67..eef6615 100644
--- a/i18n/en/settings.js
+++ b/i18n/en/settings.js
@@ -46,6 +46,11 @@ export const settings = {
     reminderText: 'Get a notification 3 days before your next period is likely to start.',
     notification: daysToEndOfPrediction => `Your next period is likely to start in 3 to ${daysToEndOfPrediction} days.`
   },
+  useCervix: {
+    title: 'Secondary symptom',
+    cervixModeOn: 'Cervix values are being used for symptothermal fertility detection. You can switch here to use mucus values for symptothermal fertility detection',
+    cervixModeOff: 'By default, mucus values are being used for symptothermal fertility detection. You can switch here to use cervix values for symptothermal fertility detection'
+  },
   passwordSettings: {
     title: 'App password',
     explainerDisabled: "Encrypt the app's database with a password. You need to enter the password every time the app is started.",
diff --git a/lib/sympto-adapter.js b/lib/sympto-adapter.js
index 821e7c5..628ea2b 100644
--- a/lib/sympto-adapter.js
+++ b/lib/sympto-adapter.js
@@ -1,6 +1,7 @@
 import getFertilityStatus from './sympto'
 import cycleModule from './cycle'
 import { fertilityStatus } from '../i18n/en/labels'
+import { useCervixObservable } from '../local-storage'
 
 export function getFertilityStatusForDay(dateString) {
   const status = getCycleStatusForDay(dateString)
@@ -48,6 +49,8 @@ export function getCycleStatusForDay(dateString, opts = {}) {
     }
   }
 
+  cycleInfo.secondarySymptom = useCervixObservable.value ? 'cervix' : 'mucus'
+
   return getFertilityStatus(cycleInfo)
 }
 
diff --git a/local-storage/index.js b/local-storage/index.js
index 5f4af70..89b37d9 100644
--- a/local-storage/index.js
+++ b/local-storage/index.js
@@ -44,6 +44,14 @@ export async function savePeriodReminder(reminder) {
   periodReminderObservable.set(reminder)
 }
 
+export const useCervixObservable = Observable()
+setObvWithInitValue('useCervix', useCervixObservable, false)
+
+export async function saveUseCervix(bool) {
+  await AsyncStorage.setItem('useCervix', JSON.stringify(bool))
+  useCervixObservable.set(bool)
+}
+
 export const hasEncryptionObservable = Observable()
 setObvWithInitValue('hasEncryption', hasEncryptionObservable, false)