Competing/training while pregnant

I've been a competitive swimmer now for 18 years (makes me feel old just to say it) and I'm pregnant with my first child. I keep reading that you don't have to modify your swimming workouts when you're pregnant, but in those same websites, I see things like "Try doing *** stroke to eliminate the strain of torso rotation" so I know they haven't the slightest clue about competitive swimming or real training. So my question is, does anyone have any good resource for how hard you can push yourself swimming while pregnant? And don't tell me to ask my doctor because I'm guessing she knows even less about swimming than "babycenter.com". My primary concern is with becoming slightly hypoxic while swimming (during flip turns and underwater pull outs). I often come up a little breathless, but am okay within a stroke or two. If I weren't pregnant, I wouldn't think anything about this, but it's hard to know if that's "bad" for the little one. Any thoughts or direction would be greatly appreciated.:drown: