When I was pregnant with my daughter I also had this. When I explained it to my ob they assumed it was some sort of infection. Possibly a small yeast infection. But I don't believe it was because for most of my pregnancy it was yellowish tan color and have gotten tons of swabs done coming back clear of everything. So if there's no itching, burning while you pee it maybe be normal and just hormones changing the color. Keep an eye on it and see an obgyn asap just to make sure!