Concentric contractions: A concentric contraction is a type of muscle contraction where the length of the muscles shorten while undergoing tension. For example, when you pick up a curl bar and perform a biceps curl, the length of your biceps muscles shorten.
Here are just a few reasons why your baby may have blood in his stool: 1  An anal fissure, which is a small anal tear often caused by passing a hard stool. 2  A food allergy. 3  Maternal blood from delivery or from cracked, sore nipples.  An intestinal 1  infection. An intestinal disorder, such as colitis or intussusception.
My baby has blood in her diaper. The same maternal hormones that cause swollen testicles and labia are also responsible for the bloody vaginal discharge that newborn girls sometimes have. Don't worry if you see a small smudge of blood or bit of staining on your baby's diaper in the first weeks of life.