When a Muslim couple is going to have sex, both husband and wife should say this dua for intercourse:
بِاسْمِ الله، اللّهُمَّ جَنِّبْنِي الشَّيْطَانَ وَجَنِّبِ الشَّيْطَانَ مَا رَزَقْتَنَا
Bismillāh, Allāhumma Jannibnish Shaitān, Wa Jannibish Shaitāna Mā Razaqtanā
Meaning: In the name of Allah. O Allah! protect me from Satan and keep Satan away from what You bestow upon us (children).
Prophet Muhammad (Peace be upon him) said: If someone says this dua when he has sex with her wife, then a child is born from this sex, satan will never harm him. (Bukhari, Hadith: 141, 3271, 5165, 6388, 7396)