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.
There are many general types of bacteria used as probiotics (two common ones are Lactobacillus and Bifidobacterium), and many different species as well as strains within species. They have different physiological effectsâand thus possibly different health benefits (as well as possible risks). Some yeasts, such as Saccharmyces, can also act as probiotics. Probiotic products may contain a single strain or many strains, and the number of organisms in a daily dose can range from 1 billion to more than 250 billion.