I thought I’d chime in. I am an on-again, off-again Bikram Yoga practitioner. I’m currently off-again since I am 28 weeks pregnant. Stay away from it during your TWW. If you were someone who had been practicing for quite some time, you would be okay to take classes just as long as you stayed very, very hydrated and didn’t push yourself to the limit. [name]Even[/name] though you sound like you’re very athletic, it’s never a good idea to start a new workout routine when you’re pregnant, especially something so intense.
Yoga in general, but in my personal opinion, Bikram yoga specifically, can be a great addition to your own personal fertility protocol. For me, Bikram yoga was very helpful when I was trying to conceive. I started up my practice again late last summer after taking a several month break. I became pregnant in early Oct. The series of postures is fantastic for supporting blood flow to your lower abdomen and reproductive organs. There are several poses that specifically target reproductive organs and the spinal nerve roots that innervate those organs. Certain poses can also increase libido. I must say, though, not everyone agrees with me. Some health practitioners, especially natural health practitioners may tell you that hot yoga is a definite no-no if you’re trying to conceive because it can be too intense. Well, I think it depends upon your health, your constitution, and your own level of fitness because it absolutely resonates with me. I don’t think there’s another form of exercise like it (and, no, I promise I am not a Bikram yoga teacher, nor do I have any connection with a Bikram studio).
If you find yourself not pregnant this month, check out a class or two. It’s definitely not for everyone, but there’s a good chance that an athlete like you will find it a bit addictive. If you practice for a few months and become pregnant, then really listen to your body. Obviously first check with your OB or midwife, and if you get the go-ahead, then take it easy with the classes. The teachers can be really helpful and will modify the poses for pregnancy if your take them aside and let them know your condition. I was able to practice into about week 10 or 11, but I ended up feeling too awful, too lightheaded, and too nauseated by the heat and the yoga room smell to continue any more. Some women do practice throughout their pregnancy, but they are better women than I because I would die if I was practicing now 
I look forward to getting back to it next fall, however, to help get back my pre-pregnancy body.
[name]Hope[/name] that helps. I feel pretty passionate about Bikram yoga and its health benefits. It’s a controversial brand of yoga, and I would have to agree with a lot of the arguments against it and against the man Bikram himself, however, it does for my body what no other exercise can do so I remain a fan.
edit: I reread your post. I thought that you ran 15-20 miles AT [name]ONE[/name] time, that’s why I kept saying what an athlete you are. Still, 15-20 miles a week is great, too. [name]Just[/name] wanted to clear that up.