After spending approximately 40 weeks inside the womb, the average newborn weighs 7 1/2 pounds. Most babies weigh between 5 1/2 and 10 pounds. The average length of a newborn is 20 inches (50 centimeters), with a range of 18 to 22 inches. The average head circumference (the distance around the head) is 14 inches (35 centimeters).
Lactobacillus and Bifidobacterium are the most common probiotic bacteria. The Lactobacillus genus has 18 different bacteria strains, while the Bifidobacterium genus consists of eight strains.
Probiotics are naturally occurring microorganisms. In most cases they are bacteria and are similar to the friendly bacteria found in the gut or skin. Lactobacillus and bifidobacterium are common probiotics that are found in many foods such as yogurt, unpasteurized milk, fermented soy and yeast, and infant formula.