Because Natural Cycles helps identify your fertile window in each cycle, you can also use the app to plan a pregnancy (by using the 'Plan a Pregnancy' mode).
After ovulation, your temperature rises due to the release of the hormone progesterone. If conception occurred, progesterone continues to produce to help with the development of the fetus. This causes the temperature to remain elevated after the expected period.
If that happens to you, Natural Cycles recognizes that conception has possibly occurred and will prompt you to take a pregnancy test for confirmation (whether you are a Plan or Prevent user).
Once you indicate a positive pregnancy test, your temperatures after ovulation will change to blue.
Example of a chart showing when you have entered a positive pregnancy test:
Once you enter a positive pregnancy test, Natural Cycles will go into the "Follow a Pregnancy" mode in the app. In this mode, instead of the daily fertility status, you will see what pregnancy week you are in, a countdown to how many days you have left in your pregnancy, conception, and due date.
Below you can see a "Follow a Pregnancy" mode screen: