Babies this young still have a very strong Moro reflex AKA the “startle reflex.” Swaddling an infant prevents that “startle” from waking up your baby, which leads to a much sounder sleep. Slight resistance in the arm span of the Zipadee-Zip really is ideal for the transition so if a baby is too tiny, the Zipadee-Zip might be a bit too big to provide that. Tip: Even if your baby is not ready to transition right now, it’s a good idea to keep a Zipadee-Zip ready to go in your nursery. The need for one will seemingly happen overnight!