The U.S. infant mortality rate has risen for the first time in more than 40 years, in large part because more women gave birth to low-birthweight infants who died before age one, according to a CDC report released on Monday, the Washington Times reports. According to the report -- titled "Explaining the 2001-2002 Infant Mortality Increase: Data from the Linked Birth/Infant Death Data Set" and conducted by CDC's National Center for Health Statistics -- there were 27,970 infant deaths in 2002, or about seven deaths per 1,000 live births. In 2001, there were 27,568 infant deaths, or about 6.8 deaths per 1,000 live births. Lead researcher Marian MacDorman said the change constitutes "a significant increase" (Wetzstein, Washington Times, 1/25). The study found that 500 more infants weighing more than one pound but less than one pound, 10.5 ounces -- defined as very low birthweight -- were born in 2002 than were born in 2001 (USA Today, 1/25). Approximately 41% of all infant deaths in 2002 were among very low-birthweight infants, according to the study (McKay, Wall Street Journal, 1/25). Researchers for the most part ruled out race, advanced maternal age and multiple births as reasons for the increase in infant mortality because the death rates rose among all racial groups, the majority of deaths occurred among infants born to women ages 20 to 34 and the infant mortality rate among multiple-birth infants declined in 2002 (Washington Times, 1/25). Overall, multiple-birth infants accounted for about 25% of all infant deaths in 2002 (Wall Street Journal, 1/25). Before 2002, the infant mortality rate had either declined or remained constant every year since 1958 (Simao, Reuters/Yahoo! News, 1/24).

Additional Explanations
Technological advancements in neonatal care also could have contributed to the increase in the infant mortality rate, according to the researchers, the Wall Street Journal reports. Fetal imaging and diagnoses allow physicians to more closely monitor pregnant women at high risk for complications, and some of these infants are delivered prematurely by caesarean section, according to MacDorman. In 2002, 57% of very low-birthweight infants were delivered by c-section, compared with about 54% in 2001 (Wall Street Journal, 1/25). Also, changes in the way hospitals report births, infant deaths and fetal deaths may have affected the infant mortality rate, according to the study (CDC release, 1/24). For instance, a fetus that dies before or during delivery is considered a fetal death, while an infant who survives delivery but dies afterward is reported as an infant death. According to the report, because more physicians deliver premature and low-birthweight babies "only to lose them a few hours or days later," it could increase the infant mortality rate, the Times reports. Preliminary 2003 data show a slight decline in infant mortality from 2002, according to the report (Washington Times, 1/25).