Americans Weigh in Over Time - Trends In U.s. Birth Weights

Americans are not born overweight. In fact, the mean birth weight of infants born as singletons (births of one infant as opposed to twins or other multiple births) has steadily declined since 1990. In 2002 the mean birth weight of all singletons was 7 pounds, 6 ounces (3,332 g), and the average white non-Hispanic singleton weighed a full 9 ounces more than the average non-Hispanic black singleton. (See Table 1.3.) The percent of infants born with higher-than-average birth weights (4,000 g or more, or at least 8 pounds, 14 ounces) declined in 2002 to 9.2 from 10.9 in 1990. (See Figure 1.2.)

While ideal birth weight varies based on the expectant mother's ethnicity, for women in the United States, the average ideal birth weight is approximately 7.5 pounds, the average weight of singletons born in 2002. In the United TABLE 1.1
Obesity prevalence among adults by state, Behavioral Risk Factor Surveillance System data by year, 1991–2001

State obesity	1991	1995	1998	1999	2000	2001
Alabama	13.2	18.3	20.7	21.8	23.5	23.4
Alaska	13.1	19.2	20.7	19.2	20.5	21.0
Arizona	11.0	12.8	12.7	11.6	18.8	17.9
Arkansas	12.7	17.3	19.2	21.9	22.6	21.7
California	10.1	14.4	16.8	19.6	19.2	20.9
Colorado	8.4	10.0	14.0	14.3	13.8	14.4
Connecticut	10.9	11.9	14.7	14.5	16.9	17.3
Delaware	14.9	16.2	16.6	17.1	16.2	20.0
District of Columbia	15.2	n/a	19.9	17.9	21.2	19.9
Florida	10.1	16.5	17.4	17.9	18.1	18.4
Georgia	9.2	12.6	18.7	20.7	20.9	22.1
Hawaii	10.4	10.4	15.3	15.3	15.1	17.6
Idaho	11.7	13.8	16.0	19.5	18.4	20.0
Illinois	12.7	16.4	17.9	20.2	20.9	20.5
Indiana	14.8	19.6	19.5	19.4	21.3	24.0
Iowa	14.4	17.2	19.3	20.9	20.8	21.8
Kansas	n/a	15.8	17.3	18.5	20.1	21.0
Kentucky	12.7	16.6	19.9	21.1	22.3	24.2
Louisiana	15.7	17.4	21.3	21.5	22.8	23.3
Maine	12.1	13.7	17.0	18.9	19.7	19.0
Maryland	11.2	15.8	19.8	17.6	19.5	19.8
Massachusetts	8.8	11.1	13.8	14.3	16.4	16.1
Michigan	15.2	17.7	20.7	22.1	21.8	24.4
Minnesota	10.6	15.0	15.7	15.0	16.8	19.2
Mississippi	15.7	18.6	22.0	22.8	24.3	25.9
Missouri	12.0	18.0	19.8	20.8	21.6	22.5
Montana	9.5	12.6	1.7	14.7	15.2	18.2
Nebraska	12.5	15.7	17.5	20.2	20.6	20.1
Nevada	n/a	13.3	13.4	15.3	17.2	19.1
New Hampshire	10.4	14.7	14.7	13.8	17.1	19.0
New Jersey	9.7	14.2	15.2	16.8	17.6	19.0
New Mexico	7.8	12.7	14.7	17.3	17.8	18.8
New York	12.8	13.3	15.9	16.9	17.2	19.7
North Carolina	13.0	16.5	19.0	21.0	21.3	22.4
North Dakota	12.9	15.6	18.7	21.2	19.8	19.9
Ohio	14.9	17.2	19.5	19.8	21.0	21.8
Oklahoma	11.9	13.0	18.7	20.2	19.0	22.1
Oregon	11.2	14.7	17.8	19.6	21.0	20.7
Pennsylvania	14.4	16.1	19.0	19.0	20.7	21.4
Rhode Island	9.1	12.9	16.2	16.01	16.8	17.3
South Carolina	13.8	16.1	20.2	20.2	21.5	21.7
South Dakota	12.8	13.6	15.4	19.0	19.2	20.6
Tennessee	12.1	18.0	18.5	20.1	22.7	22.6
Texas	12.7	15.0	19.9	21.1	22.7	23.8
Utah	9.7	12.6	15.3	16.3	18.5	18.4
Vermont	10.0	14.2	14.4	17.2	17.7	17.1
Virginia	10.1	15.2	18.2	18.6	17.5	20.0
Washington	9.9	13.5	17.6	17.7	18.5	18.9
West Virginia	15.2	17.8	22.9	23.9	22.8	24.6
Wisconsin	12.7	15.3	17.9	19.3	19.4	21.9
Wyoming	n/a	13.9	14.5	16.4	17.6	19.2
SOURCE: "Obesity Prevalence among U.S. Adults by State: BRFSS Data by Year," in 1991–2001 Prevalence of Obesity among U.S. Adults by State: Behavioral Risk Factor Surveillance System (1991–2001); Self-Reported Data, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition and Physical Activity, Atlanta, GA, 2003 [Online] http://www.cdc.gov/nccdphp/dnpa/obesity/trend/prev_reg.htm

States, the percent of babies born with low birth weight (LBW)—less than 2,500 g (5 pounds 8 ounces) has risen steadily since the mid-1980s. (See Figure 1.2.) According to data from the CDC National Center for Health Statistics the LBW rate rose from 7.7. to 7.8 percent for 2001–2002, the highest level reported in more than three decades. The percent of very low birth weight (VLBW) infants—weighing less than 1,500 g (3 pounds 5 ounces)—rose from 1.44 percent in 2001 to 1.46 percent in 2002.

LBW and VLBW are major predictors of infant morbidity (illness or disease) and mortality. For LBW infants, the risk of dying during the first year of life is more than five times that of normal-birth-weight infants; the risk for VLBW infants is nearly 100 times higher. The risk of delivering an LBW infant is greatest among the youngest and oldest mothers; however, many of the LBW births among older mothers are attributable to their higher rates of multiple births. In 2002 multiples accounted for nearly two-thirds of all LBW infants delivered to mothers age forty-five and older. Less than 10 percent of singletons born to mothers age forty-five or older were LBW compared with 8.7 percent of births to mothers less than twenty years old.

In 2002, 314,077 babies were born at low birth weights in the United States. That number represented 7.8 TABLE 1.2
Prevalence of obesity among adults, by characteristics, self-reported data, 1991–2001

	Percent obese Behavioral Risk Factor Surveillance System data by year:
Characteristics	1991	1995	1998	1999	2000	2001
Total	12.0	15.3	17.9	18.9	19.8	20.9
Gender
Men	11.7	15.6	17.7	19.1	20.2	21.0
Women	12.2	15.0	18.1	18.6	19.4	20.8
Age groups
18-29	7.1	10.1	12.1	12.1	13.5	14.0
30-39	11.3	14.4	16.9	18.6	20.2	20.5
40-49	15.8	17.9	21.2	22.4	22.9	24.7
50-59	16.1	21.6	23.8	24.2	25.6	26.1
60-69	14.7	19.4	21.3	22.3	22.9	25.3
70	11.4	12.1	14.6	16.1	15.5	17.1
Race, ethnicity
White, non Hispanic	11.3	14.5	16.6	17.7	18.5	19.6
Black, non Hispanic	19.3	22.6	26.9	27.3	29.3	31.1
Hispanic	11.6	16.8	20.8	21.5	23.4	23.7
Other	7.3	9.6	11.9	12.4	12.0	15.7
Educational level
Less than high school	16.5	20.1	24.1	25.3	26.1	27.4
High school degree	13.3	16.7	19.4	20.6	21.7	23.2
Some college	10.7	15.1	17.8	18.1	19.5	21.0
College or above	8.0	11.0	13.1	14.3	15.2	15.7
Smoking status
Never smoked	12.0	15.2	17.9	19.0	19.9	20.9
Ex-smoker	14.0	17.9	20.9	21.5	22.7	23.9
Current smoker	9.9	12.3	14.8	15.7	16.3	17.8
SOURCE: "1991–2001 Prevalence of Obesity among U.S. Adults, by Characteristics: Behavioral Risk Factor Surveillance System (1991–2001); Self-Reported Data," in Overweight and Obesity Trends, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition and Physical Activity, Atlanta, GA, 2003 [Online] http://www.cdc.gov/nccdphp/dnpa/obesity/trend/prev_char.htm [accessed December 30, 2003]

percent of all births. However, the percent of LBW babies varied by state. In 2002 Alaska reported the lowest percent (4.6) and West Virginia the highest (8.7 percent) of LBW births to non-Hispanic white mothers. Of the states that reported more than 1,000 births to non-Hispanic black women, LBW ranged from a low of 9.8 percent in Oregon to a high of 15.7 percent in Utah. (See Table 1.4.)

Birth Weight Influences Risk of Disease

Although the relationship between birth weight and development of disease in adulthood is an emerging field of research, and scientists can not yet fully explain how and why birth weight is a predictor of health and illness in later life, mounting evidence indicates that both low birth weight and higher-than-average birth weight are linked to future health. Research reveals that LBW infants are more likely than normal-weight infants to develop disease in later life. Male infants with LBW who gain weight rapidly before their first birthdays appear to be at the highest risk. Investigators hypothesize that LBW infants have fewer muscle cells at birth and that rapid weight gain during the first year of life may lead to disproportionate amounts of fat to muscle and above average body mass. Persons with LBW who later develop above average body mass are at increased risk for developing diseases such as Type 2 diabetes, hypertension (high blood pressure), cardiovascular disease, and stroke. A 1997 study published in the British journal The Lancet examined the medical records of 13,249 men and found the risk of dying from stroke or heart disease was highest for those who weighed 5.5 pounds at birth or less. Those who weighed more than 8.5 pounds at birth had the lowest rate of mortality from heart attack or stroke.

Low birth weight also was linked to childhood asthma in a U.S. study published in a 2001 issue of Archives of Pediatrics and Adolescent Medicine, which found that babies born at 5.5 pounds or less faced the greatest risk of respiratory complications such as asthma. Research also has demonstrated that both LBW and abnormally high birth weight are associated with risk of developing diabetes later in life.

Evidence also indicates that birth weight is related to risk of developing breast cancer. Valerie A. McCormack and her colleagues at the Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, investigated whether size at birth and rate of fetal growth influenced the risk of developing breast cancer in adulthood. The results of the study were published in "Fetal Growth and Subsequent Risk of Breast Cancer: Results from Long Term Follow up of Swedish Cohort," (British Medical Journal, vol. 326, no. 7,838, February 2003). By examining birth and medical records of 5,358 singleton TABLE 1.3
Rate of very low birthweight and low birthweight, and mean birthweight among singletons by race and Hispanic origin of mother, selected years 1990–2002

	2002	2001	1995	19901
Total, all races, origins2
Percent very low birthweight	1.11	1.10	1.08	1.05
Percent low birthweight	6.12	6.04	6.05	5.90
Mean birthweight (grams)	3,332	3,339	3,353	3,365
Non-Hispanic white
Percent very low birthweight	0.81	0.81	0.78	0.73
Percent low birthweight	5.02	4.96	4.87	4.56
Mean birthweight (grams)	3,392	3,399	3,416	3,433
Non-Hispanic black
Percent very low birthweight	2.63	2.57	2.55	2.54
Percent low birthweight	11.44 11.19	11.66	11.92
Mean birthweight (grams)	3,128	3,135	3,132	3,128
Hispanic3
Percent very low birthweight	0.96	0.93	0.93	0.87
Percent low birthweight	5.44	5.40	5.36	5.23
Mean birthweight (grams)	3,332	3,337	3,343	3,351
1Data for 1990 by race and Hispanic origin exclude data for New Hampshire and Oklahoma, which did not require reporting of Hispanic origin of mother.
2Includes births to races not shown separately.
3Includes persons of Hispanic origin of any race.
Notes: Very low birthweight is less than 1,500 grams. Low birthweight is less than 2,500 grams.
SOURCE: Joyce A. Martin, Brady E. Hamilton, Paul D. Sutton, Stephanie J. Ventura, Fay Menacker, and Martha L. Munson, "Table J. Rate of very low birthweight and low birthweight, and mean birthweight among singletons by race and Hispanic origin of mother: United States, 2002," National Vital Statistics Reports, Births: Final Data for 2002, vol. 52, no. 10, Centers for Disease Control and Prevention, National Center for Health Statistics, Hyattsville, MD, December 2003 [Online] http://www.cdc.gov/nchs/births.htm [accessed December 30, 2003]

females born from 1915 to 1929, the investigators determined that size at birth was associated with breast cancer in premenopausal (the stage of reproductive life immediately before the onset of menopause) women age fifty or younger—the larger and longer the baby, the greater the risk. Birth weight or size was not associated with rates of breast cancer in postmenopausal women. Among premenopausal women who weighed 4,000 or more grams at birth (8 pounds, 14 ounces) rates of breast cancer were 3.5 times higher than those women who weighed less than 3,000 g at birth (about 6 pounds, 10 ounces). The investigators concluded that size at birth, including birth weight, length, and head circumference, is associated with risk of breast cancer in women under age fifty.

The only action able to alter the birth weight of an infant is to modify weight gain during pregnancy. In 2004 health professionals concur that for normal-weight women the ideal weight gain during pregnancy ranges from 25 to 35 pounds of fat and lean mass. Further, research published in 2003 revealed that a newborn's birth weight and mother's post-pregnancy weight are influenced not only by how much weight is gained during pregnancy, but also by the source of the excess weight. In FIGURE 1.2
Percent very low, moderately low, and high birthweight births, 1984, 1990, 2002 "Composition of Gestational Weight Gain Impacts Maternal Fat Retention and Infant Birth Weight" (American Journal of Obstetrics and Gynecology, vol. 189, no. 5, November 2003), researcher Nancy F. Butte and her colleagues conducted body scans of sixty-three women before, during, and after their pregnancies and recorded changes in women's weight from water, protein, fat, and potassium—a marker for changes in muscle tissue, one component of lean mass. The researchers found that only increases in lean mass, and not fat mass, appeared to influence infant size. Independent of how much fat women gained during pregnancy, only lean body mass increased the birth weight of the infant, with women who gained more lean body mass giving birth to larger infants.

Breastfeeding is linked to improved health outcomes for all infants; however, it is especially advisable for LBW infants. For these infants breastfeeding can reduce the risk that they will develop chronic diseases in adulthood by preventing the development of above average body mass. TABLE 1.4
Number and percent of births of low birthweight, by race, Hispanic origin of mother, and state or territory, 2002
[By place of residence. Low birthweight is birthweight of less than 2,500 grams (5 lb 8 oz)]

	Number						Percent
		White		Black				White		Black
State	All races1	Total2	Non-Hispanic	Total2	Non-Hispanic	Hispanic3	All races1	Total2	Non-Hispanic	Total2	Non-Hispanic	Hispanic3
United States4	314,077	215,799	158,592	78,813	77,376	57,383	7.8	6.8	6.9	13.3	13.4	6.5
Alabama	5,825	3,140	2,957	2,626	2,620	189	9.9	7.9	7.9	14.4	14.3	7.4
Alaska	579	331	205	48	27	51	5.8	5.2	4.6	11.1	10.1	6.4
Arizona	5,938	5,039	2,608	326	310	2,415	6.8	6.5	6.7	11.7	12.2	6.4
Arkansas	3,204	2,136	1,957	1,008	1,007	169	8.6	7.3	7.5	13.6	13.6	5.5
California	33,824	25,064	9,838	3,765	3,658	15,134	6.4	5.8	6.0	11.5	11.6	5.8
Colorado	6,067	5,338	3,609	422	403	1,777	8.9	8.6	8.6	14.4	14.6	8.5
Connecticut	3,258	2,406	1,866	652	624	560	7.8	6.9	6.7	12.6	12.7	8.0
Delaware	1,102	651	553	403	403	97	9.9	8.2	8.3	14.9	15.0	7.4
District of Columbia	866	186	105	673	659	88	11.6	7.0	6.1	14.6	14.5	9.2
Florida	17,320	10,902	7,476	5,889	5,791	3,503	8.4	7.1	7.3	12.7	12.8	6.8
Georgia	11,915	5,840	4,799	5,672	5,564	1,015	8.9	6.8	7.0	13.3	13.3	6.0
Hawaii	1,450	278	219	49	48	218	8.3	7.0	6.9	10.3	10.9	9.0
Idaho	1,284	1,228	1,028	12	10	184	6.1	6.1	6.0	*	*	6.6
Illinois	14,725	9,451	6,944	4,545	4,517	2,530	8.2	6.7	7.0	14.3	14.3	6.2
Indiana	6,463	5,140	4,741	1,205	1,203	388	7.6	6.9	7.0	13.0	13.0	6.3
Iowa	2,489	2,277	2,131	130	127	149	6.6	6.5	6.5	10.3	10.2	6.2
Kansas	2,757	2,312	1,992	354	351	299	7.0	6.6	6.7	12.3	12.4	6.0
Kentucky	4,657	3,875	3,749	711	709	132	8.6	8.0	8.0	14.4	14.4	8.1
Louisiana	6,774	2,749	2,678	3,905	3,895	79	10.4	7.5	7.6	14.7	14.6	5.7
Maine	853	822	810	16	16	11	6.3	6.3	6.3	*	*	*
Maryland	6,607	3,145	2,723	3,178	3,163	418	9.0	7.0	7.0	13.1	13.2	6.9
Massachusetts	6,046	4,663	3,928	933	798	813	7.5	7.0	6.7	11.2	12.1	8.5
Michigan	10,363	6,869	6,306	3,120	3,100	458	8.0	6.7	6.7	13.9	14.0	6.3
Minnesota	4,251	3,343	3,022	520	511	284	6.3	5.8	5.7	10.7	10.8	6.1
Mississippi	4,635	1,824	1,776	2,767	2,767	47	11.2	8.1	8.2	15.2	15.2	5.7
Missouri	6,034	4,365	4,151	1,527	1,526	210	8.0	7.0	7.0	13.9	13.9	6.4
Montana	755	634	600	6	5	25	6.8	6.7	6.7	*	*	6.5
Nebraska	1,817	1,538	1,301	196	194	202	7.2	6.7	6.8	13.6	13.7	6.1
Nevada	2,445	1,843	1,093	379	370	738	7.5	6.8	7.0	14.5	14.6	6.5
New Hampshire	914	866	828	18	17	20	6.3	6.3	6.5	*	*	4.0
New Jersey	9,185	5,846	4,232	2,546	2,388	1,753	8.0	6.9	6.9	12.8	13.3	7.1
New Mexico	2,225	1,871	680	71	68	1,200	8.0	8.0	7.8	13.9	14.3	8.2
New York	19,802	12,276	8,513	5,945	5,552	4,077	7.9	6.8	6.5	12.0	12.3	7.5
North Carolina	10,514	6,238	5,332	3,875	3,860	923	9.0	7.3	7.6	14.1	14.1	6.1
North Dakota	486	412	391	12	11	11	6.3	6.1	6.0	*	*	*
Ohio	12,334	8,927	8,562	3,118	3,105	351	8.3	7.3	7.3	13.8	13.9	7.3
Oklahoma	4,019	2,946	2,593	652	646	367	8.0	7.5	7.5	13.9	13.8	7.0
Oregon	2,608	2,290	1,862	90	88	428	5.8	5.6	5.7	9.6	9.8	5.3
Pennsylvania	11,685	8,463	7,609	2,839	2,773	798	8.2	7.2	7.0	14.0	14.1	9.2
Rhode Island	1,019	823	543	123	114	173	7.9	7.5	7.4	10.8	11.1	7.5
South Carolina	5,455	2,672	2,456	2,679	2,674	216	10.0	7.6	7.6	14.7	14.8	6.8
South Dakota	765	604	582	12	12	24	7.2	7.0	7.0	*	*	7.5
Tennessee	7,106	4,593	4,347	2,370	2,359	253	9.2	7.7	7.9	14.6	14.5	5.8
Texas	28,646	22,264	9,698	5,301	5,242	12,534	7.7	7.0	7.1	12.7	12.8	7.0
Utah	3,164	2,938	2,478	49	49	451	6.4	6.3	6.3	14.5	15.7	6.5
Vermont	409	406	403	–	–	2	6.4	6.5	6.6	*	*	*
Virginia	7,888	4,615	4,025	2,781	2,763	605	7.9	6.5	6.5	12.6	12.6	6.2
Washington	4,604	3,646	2,937	344	335	651	5.9	5.5	5.5	10.2	10.4	5.3
West Virginia	1,855	1,741	1,726	96	96	7	9.0	8.8	8.7	14.2	14.2	*
Wisconsin	4,538	3,462	3,173	848	841	302	6.6	5.9	5.9	13.2	13.3	5.7

LBW infants who are breastfed for at least twelve months have about half the risk of developing above average body mass during childhood.