There were 1,900 gate related injuries requiring emergency room care in 2009. Older accordion style gates with diamond shape openings are a main culprit because they can entrap a baby's head, hand or arm. It is better to use a gate with vertical bars.
It is very important to use the right gate at the right location. Using a pressure mounted gate at the top of a stair is inadequate. A screw-in hardware mounted gate is much safer at a stair.
You also have to install the gate in a proper manner, by securely attaching it to the wall with screws that reach the underlying wall stud, or by using hollow wall anchors. Follow all manufacturer instructions when installing.
It is also good to be mindful of the small plastic parts on a gate that may break over time. Small pieces could be a choking hazard, and the gate may not work properly if a part is broken. It is a good idea to monitor product recalls in case your gate is recalled for safety reasons.
Kidsafe has put together a guide to help you choose the right gate. Guide Link