advise the government
On veiligheid.nl the government advises:
Falling down the stairs is one of the most serious accidents. It is mainly children of one and two years old who are most at risk. Never underestimate your child's entrepreneurial drive and take timely measures to prevent serious falls. As soon as a child is able to walk independently and well, it is important to practice climbing stairs with your child.
Tips especially for children:
Practice climbing stairs with your child.
Young children are often not yet able to reach the banisters. The normal banister is too high and too thick for a small child, so an extra, narrower children's banister is a good solution. This child support should be mounted at a height of 60 cm.
Don't let children walk down the stairs with stuff in their hands.Do not let children play near the stairs (especially not with a baby walker).
Child learning to climb stairs:
Teach your child to climb stairs.Let your child go up in front of you, wide side of the stairs;
Teach him, as soon as he can reach the handrail, to always hold it with one hand;
Go down the stairs in front of your child.
Don't let children go up and down the stairs on their own when they can't do it in a well-coordinated way.
As long as he cannot (properly) walk yet, your child can slide down the stairs sitting down, step by step.
Stair gate
A stair gate makes the stairs inaccessible for hummingbirds, so they can't fall off or climb on them. It is best to place a stair gate at the top and bottom of the stairs. Place the stair gates before your child can crawl and do not remove them until your child is able to climb stairs in a well-coordinated manner. And very important: always close the stair gate!
Studies have shown that parents consider the stairs to be the most dangerous.
https://www.veiligheid.nl/kinderveiligheid/kindveilig-huis/huiskamer/vaste-trap