Newborn babies have to bear the pain of so many needle pricks in form of injections right from the moment they are born until the age of 4 or 5. To reduce the pain during these routine heel-prick or needle stick blood tests, babies are given anything from sugar water, pacifier, breast-feeding to a placebo of sterile water. Out of all these pain relieving measures, research show that breast feeding is the best way to ease a baby's pain during any kind of tests.

The research conducted on 1,000 newborns found that breast milk was anyway more effective than any thing else in soothing the baby. This was because of a number of reasons including the comforting presence of the mother, skin-to-skin contact; diversion of the baby's attention; and the sweetness of breast milk.
So this comes as another reason to breastfeed your baby, at least when you are taking him to the doctor to get that painful test done.