Did David blame his mother for his sinfulness, or teach that babies are born guilty of sin in Ps.51 :5? Did he teach that everyone or anyone is born inheriting the guilt of "Original Sin"? Of course the answer is NO! In Ps.51:1-4 David confesses his OWN sin and the background of it is 2 Sam. 11,12. Yes, the various translations can be confusing. But note the ASV reads, "Behold, I was brought forth in iniquity, and in sin did my mother conceive me." This did 't say David was born guilty of sin, but he was "brought forth" into a sinful world. His mother "conceived" him in a sinful world. This verse does not have David guilty of doing anything. His birth was not a sin! It was certainly not his choice! Ps.51:5 is an overstatement like Vs.4 where he says he only sinned against God, but in truth he had sinned against Uriah and Bathsheba too.
The Psalms are poetry! Everything David says must be taken in context like all Bible verses. David knows God is just and does not judge people for the sins of another! The Law of Moses forbids holding a child guilty for their parents sin (Deut. 24:16, 2Chron. 25:4, Eze. 18:3,20). Jesus also used the pure, innocent, and dependent children as a contrast with guilty sinners who must choose to repent and become like these children to enter the New Covenant Kingdom He is establishing Matt. I8:10; 19:14. Of all the things David says, he is certainly not blaming his mom or anyone for his own guilt! Again, this is poetry and David's way of saying just how awful and treacherous HIS SIN was and how it had crushed his soul! It is incredible how one verse, Psalm. 51:5 could establish blasphemous doctrines like "Total Hereditary Depravity" etc.