So, let's say that you were standing next to the crib in which your two are children playing. And lets say that the 3 year old climbs in and out of the crib with no difficulty because he's tall and his legs can reach over the rail and he's agile and has more control of his motor skills. Then, let's say that the still-1-but-almost-2 year old tries to do it too. And let's just assume that it was only by the grace of God that you (me) were (was) standing right there to catch the plummeting little girl before causing a spinal cord injury.
A. Assume this only happened because the mom-safety-net was right there, and gave her the courage to attempt it, and it will never happen again, certainly not when mom is out of the room.
B. Have visions all night about the broken arms and plan out how you would handle the resulting injuries in the middle of the night, like: visualizing where a magazine is to use as a splint, remembering where your jeans are for a trip to the hospital, maybe making sure your hooded sweatshirt is by the door.
C. Put the mattress on the floor and start shopping for a big girl bed.
D. Ask The Internet what to do.
I can tell you I am hoping for A, and I did B, and now I'm doing D in case I should be doing C.