I'm due today and I've been to the beach plenty of times :) make sure you put sunblock on ur tummy so it doesn't burn, and if it's really hot out drink plenty of water to keep yourself hydrated !
I don't think it will make stretch marks, but if you have new ones or get some down the road, it may be a different color until it fades. As long as you use lotion and don't get burnt up, along with staying hydrated out there, I'd say you're good. Sun poisoning is what's dangerous.
Theres nothing wrong with it, your skin is more sensitive so its easier to get burnt. Try it, you just might not enjoy as much as you used to, I went to the river and laid out last weekend and oh man I got so hot I wanted to throw up. It was yucky. You already have an elevated temperature so the sun just makes you feel extra hot. I used to love sun bathing.
Oh and PS. Stretch marks are from your skin stretching, and they are a part of your genetics. Some people get them, some don't, they're inevitable. There is no way sun bathing will give them to you.
Okay thanks ladies. Yeah stretch marks don't run in my family so hopefully I don't get them but I think ill just chill at the pool so I can jump in if it gets too hot.