Vaginal swelling in 38th week of pregnancy?

I believe you are referring to the phenomenon known as "cheeseburger crotch." It is so named because it looks (and smells, sometimes) like half a cheeseburger. Totally normal, just due to hormones, pooling blood, and pressure from the weight of the baby.

If you're just getting this now, you're lucky. Usually it shows up even earlier.

Vaginal Swelling In Pregnancy

Very common particularly late in pregnancy. I understand it is caused by a combination of hormones and the downward pressure that the weight of the baby places on your uterus and nether regions. If you peeked down there you'd probably also see it is pinker / redder than normal.

It will resolve after you give birth, quite quickly in fact. Best of luck!

This happened to me and I read that this happens during the late stages of pregnancy. It wasn't a sign of early labor for me. My doctor told me the hormones made it puffy. I just put a warm compress on it for a few minutes and it helped. Good luck!