When a baby lies down to sleep he loses the beneficial effect of gravity, which helps keep the stomach's contents in the stomach. Oftentimes, nights are the worst times for children suffering from acid reflux.
A common suggestion to reduce nighttime effects of reflux is to have the baby sleep on an incline so that the feet of the baby are lower than its head. Usually this is done by tilting the baby's mattress, which is easiest and safest. Or you could tilt the crib.
Regardless of the method, you are looking to elevate the head of the baby at about a 30° to 45° angle higher than his feet.
Method 1: Tilt the mattress.
With most cribs, you can change the height of the mattress by simply raising or lowering the mattress's supporting platform. Remove the sheets and mattress covering, and then remove the mattress. The mattress will be resting on a supporting platform (may be solid or springs). Where this platform attaches to the crib-frame there may be attachments that allow you to lower the mattress as the child grows older. While maintaining the head portion of the mattress in its current location, lower the feet portion one or two positions.
If there are not attachments to lower the mattress-supporting platform, you can still tilt just the mattress by inserting pillows or blankets under the mattress. It is of utmost importance that if you do this, you do not cause the mattress to bend in the middle, but instead try to have the entire mattress flat but tilted.
Method 2: Tilt the crib.
If either of the above methods don't work, or if the elevation is maximized, you may need to tilt the entire crib. Be careful. Doing this may cause the crib to be rather unstable.
If the crib legs have wheels on them, remove the wheels. This will make the crib more stable. Now place solid supports under the two legs of the head-end of the crib. The supports must be solid so that they do not compress or break. We have found that bricks with holes in them allow us to elevate the crib, while keeping the legs stable because the legs sit in the holes. Depending on your crib, a height increase of about 6 inches or so may give you the appropriate tilt angle.