It could be your prenatal vitamins. I've heard some people say it makes their urine dark and others say it makes it bright. Or it could be that you need to drink more water. There's a ton of reasons for changes in urine color.
That makes me feel better!
My urine did the same and I don't have GD. It was almost clear during the first 10 weeks of pregnancy then got super dark, then normal yellowish, then super dark again now its almost clear and I'm 39 weeks. I thought maybe I had a UTI or was dehydrated but they checked and nothing. So who knows.
Your body needs more water as you get further along. I'd say just drink more water. Also could be the pre natal vitamins. Iron makes urine darker