Knowing exactly when to lower crib mattress settings is a critical safety decision that evolves as your baby grows and develops new movement skills. Most parents start with the mattress in the highest position for easy access to their newborn, but this convenient height quickly becomes unsafe as your baby begins to move independently. Timing these adjustments correctly prevents dangerous falls while balancing your need for comfortable access to your little one.
Watch for movement milestones
The first mattress adjustment typically coincides with your baby’s initial mobility developments. While every child develops at their own pace, certain physical milestones signal the need for lowering the mattress:
- When your baby can push up on their hands and knees (around 4-5 months)
- When they can sit up with support (around 5-6 months)
- When they can pull themselves to a standing position (around 8-9 months)
- When they can stand unassisted (around 10-12 months)
These movement capabilities dramatically change the fall risk calculation. A baby who can roll might accidentally roll against the crib side, while a baby who can pull to stand might climb over the rail entirely. The American Academy of Paediatrics recommends lowering the mattress before your baby reaches each mobility milestone rather than waiting until they’ve demonstrated the skill. Many parents are surprised by how quickly their babies develop these abilities. What seems impossible one day might be your baby’s new favourite skill the next morning. This unpredictability makes proactive adjustment essential for maintaining a safe sleep environment.
Three-stage approach
Most modern cribs feature three distinct mattress height positions, each designed for a specific developmental stage. Following this progression offers the best balance of safety and convenience:
- Highest position: Appropriate only for newborns with no mobility (0-4 months)
- Middle position: Suitable once baby can push up or roll over (4-6 months)
- Lowest position: Required when baby can sit up or pull to stand (6+ months)
Transitioning from the highest to middle position often feels premature to many parents. Still, this early adjustment provides a crucial safety buffer when rolling and pushing up skills are developing rapidly. The middle position maintains relatively comfortable access for parents while preventing the baby from rolling out. The transition to the lowest position might seem excessive when your baby is just learning to sit, but babies often progress from sitting to pulling up in weeks. The lowest position ensures that even if your baby stands at the crib rail, the height will extend well above their chest level, preventing climbing attempts.
Toddler bed transition
The final mattress adjustment comes when your crib converts to a toddler bed, typically around 2-3 years old. This transition becomes necessary when your child shows signs of attempting to climb out despite the lowest mattress setting. Signs that it’s time for the toddler bed conversion include a leg consistently hooked over the rail, verbalised intentions to climb out, or any successful escape attempt. Converting to a toddler bed before a fall occurs prevents injuries while honouring your child’s developing independence.
The safest approach involves monitoring your child’s physical abilities and interest in climbing. Some physically capable children never attempt to climb out, while others seem determined to escape from a very early age. Both developmental milestones and individual temperament should guide your timing for this final transition.
