40 +3 and baby is measuring 10 lbs 15 oz

I know ultrasounds can be off but the doctor already said last week she feels a big baby in there and then the u/s today showed that measurement. They said they can be off as much as 2 lbs. Even so it looks like I may have a 9 pounder conservatively. I was just curious who all out there has given birth to big babies vaginally and was there much tearing? I've been advised to put coconut oil on my perineum to aid in not tearing during labor.