It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When any of you goes to his wife, let him not forget to say: 'Bismillah (In the name of Allah); O Allah, keep me and what You have granted me away from the accursed Satan.' Then, if it is decreed that a child is born to them, Satan will never harm it."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7808