I'm actually in this scenario right now, started taking synarel 3 days ago and although a very slim chance, there is still a chance that I could be prg naturally from our clomid cycle last month. Because of the xmas/new year public holidays I actually started synarel on cd19, so it's just way too early to even do a hpt. There's no way of knowing.

Our FS discussed this possibility with me and told me that it doesn't harm a pregnancy "as far as they know" and that's he's certainly had patients who've taken synarel without knowing they were prg and it had no ill effect. He did say that no big studies had been done into it (which I thought was a bit strange actually, considering the likelihood of this happening) but overall, he didn't seem concerned about it.

So I've decided not to be concerned about it either, we've only got about a 5% chance of natural conception anyway and I wanted to start my IVF cycle. Pretty sick of waiting around and putting plans on hold on the basis of 'what if's.

I'd definately discuss it with your FS/ob though.