Is it true that it is not permissible to approach one's wife on Wednesday night, and that if the wife speaks during intercourse, a defect will appear in the offspring?

A man is permitted to have intercourse with his wife at any time, except during menstruation or post-childbirth bleeding (nifas (definition)). The evidence for this is Allah’s saying: "Your wives are a place of cultivation for you, so come to your cultivation however you wish." As for speaking during intercourse, some scholars have stated that it is disliked, citing a weak hadith (definition) that Al-Albani described as reprehensible and not constituting a valid proof.