As the Director of the Baby Holy Yoga program, I read lots of books on yoga and babies. Most, if not all, books tell you to not practice yoga with your baby when they are crying. I understand the concept behind not forcing a baby to practice yoga when they aren’t ready, but I’ve also found that some moments of crying are the best time for yoga. I think it all comes down to the type of crying--crying due to hunger, crying due to falling, crying due to injury, crying due to fussiness, crying due to not getting their way, crying during a tantrum.
I typically only try yoga with my crying baby if she is fussy or throwing a tantrum. One yoga technique that works well is "drops". Drops mean that you hold your baby as you stand up, you then quickly “drop” your arms down, which causes the baby to “drop”. Please note, you are always holding your child securely! I have found that these movements can take a child out of the constant cycle of crying into experiencing something new. Many times they forget about why they were even crying.
This is not always fool proof. There have been times I have tried drops or swinging my baby and it only makes her cry louder. When this occurs, I use cuddling instead of redirection to bring her comfort.