Many women will have a successful VB after a 3rd or 4th degree tear but it really needs to be a decision made in conjunction with your OB and midwife. Sometimes a CS is recommended to avoid the risk of further trauma which may not heal as well as the first one, and sometimes as a routine recommendation with no thoughts to individual circumstances. I hope you have some clarity one you have your notes from your ex-ob and can make a decision that you are comfortable with.