diff --git a/lib/sympto-adapter.js b/lib/sympto-adapter.js
index 2991da9..f2fb1c0 100644
--- a/lib/sympto-adapter.js
+++ b/lib/sympto-adapter.js
@@ -108,7 +108,11 @@ function formatCycleForSympto(cycle) {
       if (day[symptomName] && day[symptomName].exclude) {
         delete day[symptomName]
       }
-    });
+    })
+    // remove days with incomplete cervix values
+    if (hasIncompleteCervixValue(day)) {
+      delete day.cervix
+    }
     // change format
     ['bleeding', 'temperature', 'mucus'].forEach(symptomName => {
       if (day[symptomName]) day[symptomName] = day[symptomName].value
@@ -119,4 +123,8 @@ function formatCycleForSympto(cycle) {
   // we get earliest last, but sympto wants earliest first
   formatted.reverse()
   return formatted
+}
+
+function hasIncompleteCervixValue(day) {
+  return day.cervix && (typeof day.cervix.opening != 'number' || typeof day.cervix.firmness != 'number')
 }
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