I had one done at 26wks and it actually came out very good we got good pictures of her face, im getting another one done this wk (36wks) so hope its even better
yeah, the place we're going to says weeks 28-34 there - so it's about the same as @keaij said!
around then is when they say the baby has plenty of room still & has enough of the cute "baby fat" on them for good pictures!! ((:
I went to the 3d/4d place at 16 weeks, and the lady told me anywhere from 29 weeks to 35 weeks is perfect, because the baby is fully formed.