Baby sleep sacks have been popular in Europe for the last few decades but are just starting to be used in other areas of the world such as America.
They are also called baby sleeping bags, but it is important not to confuse them with the kind of sleeping bag that campers use.
A baby sleep sack or sleeping bag is intended to be used in a relatively warm indoor environment rather than outdoors and thus is not as warm as a hiker's sleeping bag.
It has sleeves or holes for the arms but also come with snaps on the shoulder straps for ease of removal.
These bags are popular for a number of reasons, the main one being that an infant can't kick off the covering as it can with blankets, so parents can be sure the baby stays warm throughout the night.
They also keep babies from scratching itchy insect bites or rashes, and the coziness of a baby sleeping bag tends to help a baby fall asleep more easily, and go back to sleep more quickly if it wakes up during the night.
Factors to consider when purchasing baby sleep sacks: First, the sack should not be too warm.
Baby sleeping bags are assigned a number known as a TOG rating, which goes up as the warmth of the bag increases.
In temperate climates with an average level of heating in the sleeping area, a TOG of around 2.
2 to 4 is appropriate in the winter, and below that in the summer.
You can always add a sheet on top of the bag if you feel the room temperature is extra cold.
The holes for the arms should be loose enough to allow air circulation.
Second, the sack should be neither too big, allowing the possibility that the baby's head could slip inside, nor too small, preventing free movement of the legs.
Third, the material should preferably be cotton or fleece.
Quilted materials are normally too hot.