It's safe, and is actually recommended to help with any swelling in your vagina caused by the increased level or hormones, if you find you're having a hard time because of your belly, try using a pillow to support yourself :)
If you have a high risk pregnancy you should talk to your doctor about sex first. Otherwise, it should be safe and harmless.
Perfectly safe.
Its great to do it later in in pregnancy as well to help prep your cervix for labor.