Hopefully this beta will help some other pregnant climber out there. :o)
To belay comfortably, loosen the strap directly above your hip so the tie-in point is high and looser at your breastbone, with the red belay loops close together. Also, don't belay (toprope) climbers that are significantly larger than you are, as this adjustment transfers more pressure to your mid-back, instead of around your legs.
This is the intuitive way to adjust the harness, but it compresses your rib cage and prevents you from raising your legs. Result: if climbing, you can't breathe while weighting the harness, and you can't keep your face/ belly off the rock while being lowered.
To climb comfortably, cinch the straps directly above your hips down as far as reasonable. This separates the tie-in points and pulls them low across your belly, but it also transfers more weight to the straps around your legs and lower back. If I rest or fall, the tie-in point rises to the level of my sternum and doesn't crush the bump.