I don't necessarily see an issue, but it seems like it would be challenging in terms of when to disclose. I certainly don't think you'd want to lie or hide it, but I can also see you might not want that to be the first thing you tell them.
When DH was single, he did some online dating and went on a date with a woman who turned out to be 7 or 8 months pregnant, and hadn't said anything prior to their date. Needless to say, he was a bit shocked and the date did not go well. I think the further along you are, the more necessary it is to say something in advance.
I wouldn't judge a single mother and I definitely wouldn't judge a single pregnant woman's dating choices. I totally agree with PP though--disclosure is key. It would definitely be jarring to show up for a date only to be met with a baby bump. That being said, the increase in boob size could very well make up for it.
Re: Dating while pregnant
When DH was single, he did some online dating and went on a date with a woman who turned out to be 7 or 8 months pregnant, and hadn't said anything prior to their date. Needless to say, he was a bit shocked and the date did not go well. I think the further along you are, the more necessary it is to say something in advance.