Praise be to Allah;
Among the manners prescribed by the shari’ah is that the Muslim should say when he commences intercourse with his wife:
"bismillaah, oh Allaah, shield us from Satan and keep him away from us and from what You [may] bestow upon us (i.e. children)" narrated by Al-Bukhari, Fath ul-Baari # 138
[transliteration: "bismillaah, allaahumma jannibnash-shaytaana wa jannib-ash-shaytaana maa razaqtana"]
This opening invocation is useful in that if Allaah blesses the husband and the wife with a child, this child will not be harmed by Satan.
As for what is to be said by the husband when consummating the marriage with his wife,(please refer to Question# 854 which has been answered previously) .