When new moms-to-be are filling out their baby registry or shopping for everyday infant must-haves, they often overlook a very important item: the portable playpen.

It's hard to look at a helpless, wrinkled newborn and understand that within a matter of a few months, she'll start to roll over, which will lead to sitting up, which will lead to crawling or scooting...you get the picture. In under a year you'll have a super-active ball of energy that needs constant supervision and guidance.

A portable playpen, often referred to as a Pack and Play (a model name created by Graco, a major producer of portable playpens), is similar to a traditional playpen in most ways. It has a cushioned floor and four netted sides to keep baby safely contained. It allows a parent to do housework, chat with a friend, or catch up on some work online without the constant worry of losing track of a mobile infant.

The only difference is what the name implies: portable playpens can be folded into a neat, rectangular package and brought along on family vacations, play dates, or wherever life calls.

The ease with which these portable playpens can be folded, carried, and reopened is usually their most important selling point. Any parent who's owned a portable playpen will tell you that some of these models require more time and brute strength to open than the average mom wants to expend on a relaxing afternoon.

There are also other considerations for parents in the market for portable playpens, such as comfort, size, and overall appearance. Some products also have extra features like attached changing tables or bassinets.

As with any other product we use around our children, safety is always the biggest concern when it comes to portable playpens. The most common safety hazard for this type of product is faulty latches. If the parts that hold up the portable playpen's walls malfunction, the resulting collapse can be dangerous for the baby inside. This was the case in the Kolkraft recall of 2009.