The Prophet (Sallallähu alaihi wa sallam) said, “If anyone of you on having sexual relations with his wife said (and he must say it before starting) ‘In the name of Allah.
O Allah! Protect us from Satan and also protect what you bestow upon us (i.e. the coming offspring) from Satan, and if it is destined that they should have a child then, Satan will never be able to harm that offspring.”

[Bukhari 0143]