The State of Our Health - Children's Health: Low-birthweight

Children's health begins before birth. Low weight at birth (less than 2,500 grams, 5 lbs. 8 oz.) is not only the cause of 70% of infant deaths and a third of all handicapped conditions, it also affects the life of the child as an adult — for the worse. Low-birthweight is usually abbreviated as LBW.

Trends in low-weight births have not changed much in the last 30 years despite dramatic increases in multiple births (one cause of LBW). Among whites, 6.5% of all live births are low-weight. Among blacks this figure is 13.0%. The rate is very high — it is higher than the low-birthweight ratio in Rwanda in 1992 (11.7%) — and is another indicator showing the generally poor state of health of black Americans.

Causes. In 2000, 44% of LBW births were premature — the baby born before the 37th week of gestation. LBW is also associated with multiple births — which have been increasing rather dramatically — 26% for twins, 138% for triplets, 174% for quadruplets, and 492% for higher-order multiples in the 1990-2000 period. Many such births are due to new medical interventions ("assisted reproductive techniques," ART).

Low-birthweight singletons, when born at normal term, suffer from intrauterine growth retardation — which is due to many factors, including maternal malnutrition, anemia, infectious disease (not least those sexually transmitted and those of the urinary tract), kidney disease, high blood pressure, and other ailments of the mother. The mother is often underweight at conception and does not gain sufficient weight as pregnancy progresses. The fetus also may have genetic/chromosomal defects.

Very young mothers (under 15) and those at the end of their reproductive cycle (45+) have the highest percentage of LBW babies. Women who smoke, drink alcohol, and take drugs put their babies at risk. Low-birthweight girls survive to give birth to LBW babies themselves. There is a definite cycle to this phenomenon, observable especially in under- developed regions of the world or in communities in the U.S. that resemble them.

Consequences. Low-birthweight has been found to impair the immune system. LBW children may experience poor cognitive development. Those who survive into adulthood are more at risk for developing chronic diseases. Dr. David J.P. Barker, a British physician, first proposed the "fetal origins of disease hypothesis," also known as the Barker hypothesis. The hypothesis states that:

"… fetal undernutrition at critical periods of development in the intrauterine environment and during infancy leads to permanent changes in body structure and metabolism. These changes result in increased adult susceptibility to coronary heart disease and non-insulin dependent diabetes mellitus. There is also growing evidence that those adults born with low birthweight suffer an increased risk of low blood pressure, obstructive lung disease, high cholesterol and renal damage."⁷

Thus childhood — indeed prenatal — problems cast their shadow over later life.

American Indians and Alaskan Natives have a slightly higher rate of LBW births than whites. In 1999, their rate was 7.15% of live births versus a white rate of 6.57%. Asians and Pacific Islanders have a rate slightly higher than American Indians, 7.45% in 1999. Within this group, those of Chinese extraction had the lowest rate of any racial group,5.19%; Filipinos had the highest rate--second only to blacks--of 8.3%.

In 1999, cigarette smokers as a group had a 12.1% rate, nonsmokers 7.2%.

Sources: Centers for Disease Control and Prevention. Health, United States, 2001. For 2000 data: National Vital Statistics Report. v. 50, no. 5. 12 February 2002.