Tuesday, January 25, 2005

The U.S. infant mortality rate has increased for the first time in more than 40 years, primarily because more women gave birth to tiny babies who didn’t survive, a federal report said yesterday.

Early data for 2003 suggests that this trend may not be continuing, according to a report from the Centers for Disease Control and Prevention’s National Center for Health Statistics (NCHS).

Researchers, however, said more studies are needed to understand why so many more tiny babies are being born but not living long.

Since 1958, U.S. infant mortality rates have been declining, thanks to medical advances in saving babies with low birth weights and national campaigns urging pregnant women to seek regular prenatal care and avoid using tobacco, alcohol and drugs.

In 2001, 27,568 infants died before their first birthday, resulting in an infant mortality rate of 6.8 deaths per 1,000 live births.

However, in 2002, there were 27,970 deaths or 7 per 1,000 live births — “a significant increase,” said Marian F. MacDorman, lead researcher in the NCHS study.

A closer look at the data showed that in 2002, the number of babies born with very low birth weights, ranging from 1 pound, 1 ounce to 1 pound, 10.5 ounces, increased by nearly 500.

Modern medicine can sometimes save these tiny babies, but most die, often within a week. The 2002 data showed that 81 percent of the increased infant deaths that year were among babies weighing less than 750 grams (about 1 pound, 10.5 ounces).

Researchers generally ruled out race, age and multiple births as explanations for the rise in the mortality rate in 2002: The rates rose among all racial groups; most of the mothers whose infants died were in their prime child-bearing years of 20 to 34, not high-risk groups such as teenagers or women 35 and older; and the mortality rate for multiple births dipped in 2002.

Other possible explanations for the 2002 rate included increases in pregnancy complications, premature births and Caesarean-section deliveries, the NCHS report said.

More mothers-to-be, for instance, were experiencing anemia, hypertension, diabetes or other medical conditions that complicate pregnancy and may lead to premature births, the report said.

Premature infants are at higher risk of dying than full-term infants, and the number of premature babies, especially those born at less than six months’ gestation, increased in 2002.

In addition, more doctors are using modern fetal imaging technology to monitor mother and child. In cases of high-risk pregnancies, this information may persuade doctors to order an early Caesarean-section delivery, even though it results in a baby with low birth weight.

Finally, it is plausible that efforts to save premature infants is causing a shift in how deaths are reported, the report said. If a baby dies before or during delivery, it is reported as a fetal death; if the baby is delivered alive and dies, it is deemed an infant death. As more doctors deliver more tiny babies alive only to lose them a few hours or days later, it conceivably could push the infant mortality rate higher, the report said.

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