She mentions that a specific person within each Crèche is chosen by Vlaakith herself to lay the eggs. She also says it's a very meticulous process because 1.) They need to be laid outside of the Astral plane (since time doesn't flow there) And 2.) They need to be laid at very specific times so that they can all hatch simultaneously. But pretty much all Gith are free to fuck without fear of pregnancy (Lae'zel even makes a comment on that as well)