Most importantly, I think, is to relax into the poses and NOT stress yourself out over having a baby. Instead use this time (especially with legs on wall pose) to visualize having a baby or being pregnant. Use all five senses. If it's getting pregnant (and not just having a baby, which could include adoption) you might imagine the sounds, smells, tastes, feel, and sight of you carrying a child in your womb. Perhaps even caress your belly with gratitude that you have a baby growing inside of you.
The keys are:
2. Extend gratitude as if you are pregnant now
3. Express love for this soon to be born child
Watch out for negative feelings and do NOT focus on the lack of not having a child yet. In my opinion, these steps while resting in one of the three yoga postures (legs on wall, goddess/cobbler, and/or bridge) would be worth a try for at least a month.
Finally, if you pray or attend a church (or something similar) that offers prayer requests, then use this too--but remember to focus on the having of a baby or being pregnant or giving birth to a healthy child. I've heard of a couple of folks conceiving through prayer.