If he prostrates in prayer as a prostration of gratitude, does his prayer become invalid?

The questioner : May Allah reward you. If he prostrates in prayer, a prostration of gratitude, other than the prostration of recitation?

The Shaykh : Yes.

The questioner : As if he were given the news of a child, does his prayer become invalid?

The Shaykh : Yes, if he prostrates for gratitude while not in prayer, and he is praying, then his prayer becomes invalid because he added a prostration to it that has no reason for it in the prayer.