Follow these four steps to swaddle your baby safely:
Lay out a lightweight blanket— about 42 inches square—in a diamond shape. Fold the top corner down and lay your baby on it, her shoulders at the fold.
Holding her left arm straight at her side, pull the right top corner of the blanket down and across her body and tuck it under her tightly.
Fold the bottom of the blanket up and over your baby's bent legs, then tuck the extra fabric into the top of the blanket, under your baby's chin.