The Physics
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Mass of a Newborn Baby

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Bibliographic Entry Result
(w/surrounding text)
Merki, Don, & Mary Bronson Merki. Health: A Guide to Wellness. USA: Glencoe/McGraw Hill, 1989 "End of Ninth Month… Weighs 7 to 9 pounds (3,175.2 to 4,082.4 g)" 3–4 kg
"Baby." World Book. 2001 Edition. Chicago: World Book, Inc., 2001. "The average weight for a baby at birth is 7.5 pounds (3.4 kilograms)." 3.4 kg
Beers, Mark, & Robert Berkow. The Merck Manual of Diagnosis and Therapy.USA: Merck Research Laboratories, 1999 "The average weight for term infants is 7 lb (3.2 kg)." 3.2 kg
Berkow, Robert. The Merck Manual of Medical Information, Home Edition.New York: Pocket Books, 1997 "The average weight at birth is 7 pounds, and the average length is 20 inches." 3.18 kg
Eisenberg, Arlene, Heidi Murkoff, and Sandee Hathaway. What to Expect the First Year. New York: Workman Publishing, 1996 "Weigh baby (average weight is 7.5 pounds: 95% of new babies weigh between 5.5 and 10 pounds." 3.4 kg
2.5–4.5 kg

A newborn is a baby who is less than one month old. Shortly after birth, a doctor usually gives the newborn a thorough physical examination to assess its condition. Three of the more important measurements are body length from cown to heel, head circumference, and mass. A newborn's mass at birth is often an important indicator of its health and developement. Smaller masses may be clues to maternal intrauterine infections or chromosomal abnormalities. More massive babies may have mothers who are diabetic, hanve congenital heart disease, or who are obese.

Newborns are nourished from their mother's milk or from a bottle because they can only swallow liquids. Since newborns can only digest about 30 milliliters of mother's milk or formula at a time, they must be fed often, usually about every 4 hours. They can lose as much as 10% of their body weights in the first few days after birth because they need more food than they can consume. At about the tenth day of life, the newborn regains the lost weight and starts to gain about 28 grams per day.

Although the mass of the newborn's brain is about 25% of its final adult brain mass, the mass of the newborn's body is only about 5% of its adult mass. Obviously, a newborn's mass increases with age. However, diffeent parts of the body grow at different rates. For example, the head grows less than the rest of the body and becomes proportionally smaller over time.

Leah Oppenheim -- 2002

Bibliographic Entry Result
(w/surrounding text)
"Weight and Measurements." Maternal Newborn Nursing: A Family and Community-Based Approach. 6th ed. New Jersey: Prentice Hall, 2002. "The normal full-term Caucasian newborn has an average birth weight of 3405 g (7 lb, 8 oz.). Newborns of African and Asian descent are usually somewhat smaller." 3.4 kg
"Baby." World Book. 2nd ed. Chicago: World Book, 1998. "The average weight for a baby at birth is 7.5 pounds (3.4 kilograms)." 3.4 kg
Dickinson, Elizabeth, & Schult, Martha. Clinical Companion to Maternal-Infant Nursing Care. Missouri: Mosby, 1998. "Neonate will demonstrate norms related to: measurements: weight: 2500 g�4000 g. Weigh on balanced scale." 2.5�4 kg
Christopher, Gloria. Nurse, Interfaith Medical Center. Telephone Interview, 28 May 2002. "The average weight of a newborn baby is 6 lb., 5 oz." 2.6 kg

We have all seen babies before but do we know the characteristics of newborn babies? Babies develop and grow in different rates and manners, however, the average weight for newborn babies is pretty much consistent. The average weight for a baby at birth is approximately 3.4 kilograms. Newborns range in weight from 2.5 kilograms to 4 kilograms. This average weight is typical for a normal full-term Caucasian newborn. African American and Asian newborns have a slightly smaller weight at birth. The slight difference in the birth weight of these ethnic groups may be due to age and size of parents, health of mother, and interval between pregnancies. Within the first three or four days the newborn experiences weight loss of 5% to 10%. This weight loss is the result of fluid shifts. Large babies usually lose more weight. However, if weight loss is greater than 10%, problems can occur. A newborn's body weight is composed mostly of water. Water makes up approximately 80% of a newborn's weight. After the first week and up to six months after birth newborns also gain about 0.198 kg a week. A premature baby weighs less than 2.7 kg. Although the weight of babies vary, the average birth weight of 3.4 kg remains relatively constant.

Amanda Thomas -- 2002