Preemies Raise U.S. Infant Mortality Rate

High Percentage of Premature Births Contributing to Nation's High Infant Mortality Rate, Report Shows

By Bill Hendrick
WebMD Health News

Reviewed By Louise Chang, MD

Nov. 3, 2009 -- The high percentage of preterm babies is the main cause of the high infant mortality rate in the U.S., the CDC says in a new report.

The U.S. "does a good job of saving babies when they are born preterm," Marian F. MacDorman, PhD, of the CDC's National Center for Health Statistics, tells WebMD. "The problem we have is prevention, preventing that preterm birth, and that's where we are in trouble, I think."

Based on 2005 data, one in eight births in the U.S. was preterm, compared with one in 18 in Ireland and Finland, says the report in the CDC's NCHS Data Brief No. 23.

In the U.S., 6.9 babies died out of every 1,000 live births, placing America near the bottom in a comparison of selected countries.

Infant Mortality Rate per 1,000 Live Births

Here are infant mortality rankings, showing the U.S. ranking far below countries in Europe and the Far East.

Singapore 2.1

Sweden 2.4

Hong Kong 2.4

Japan 2.8

Finland 3.0

Norway 3.1

Czech Republic 3.4

Portugal 3.5

France 3.6

Belgium 3.7

Greece 3.8

Germany 3.9

Ireland 4.0

Spain 4.1

Switzerland 4.2

Denmark 4.4

Israel 4.6

Italy 4.7

Netherlands 4.9

England and Wales 5.0

Australia 5.0

New Zealand 5.1

Scotland 5.2

Canada 5.4

Hungary 6.2

Cuba 6.2

Northern Ireland 6.3

Poland 6.4

United States 6.9

Slovakia 7.2

Preterm Births Driving Infant Mortality Rate

MacDorman tells WebMD "the climate of medical management has changed over the past 15 to 20 years" in the U.S. "Back in the day, if a woman had high blood pressure, they might put her in the hospital and wait until the baby is more mature. Now the docs seem more likely to want to deliver the baby early."

She says infant mortality in the U.S. is a "major public health problem, and it's not improving."

The U.S. infant mortality rate, MacDorman and colleagues report in the article, is mainly attributable to an increase in preterm births. Preterm births are at much higher risk for death or disability than full-term births.

"We don't know why the preterm rate is so much higher than in Europe," MacDorman tells WebMD. "But teens, older mothers, smokers all have higher preterm rates." The percentage of preterm births in 2004 was 12.4% for the U.S., which was much higher than the selected European countries, such as 5.5% for Ireland, 6.3% for France, and 8.9% for Germany.

When births after less than 22 weeks are excluded, the U.S. and other countries show a drop in infant deaths in 2004. However, the U.S. still has an infant mortality rate higher than most European countries, with nearly twice the rate of Sweden and Norway.

Since 1960, the infant mortality rate in the U.S. has been worsening, the researchers report. The U.S. international rate was 12th in 1960, fell to 23rd in 1990, to 29th in 2004 and 30th in 2005. In that year, 22 countries had infant mortality rates of 5.0 or lower per 1,000 live births.

The researchers say that some countries have limits on birth registration requirements, and very small infants who die soon after birth are excluded in some data.

"The majority of infants born at 22-23 weeks of gestation die in their first year of life," the article says.

Even for full-term infants, the U.S. rate was high at 2.4 per 1,000 births, compared to other countries.

Infant Mortality Rate for Full-Term Births

This list shows infant deaths per 1,000 live births at full-term, or 37 weeks or more.

Finland 1.4

Norway 1.5

Sweden 1.5

Austria 1.5

Northern Ireland 1.6

Scotland 1.7

England and Wales 1.8

Poland 2.3

Denmark 2.3

United States 2.4

SOURCES: News release, CDC.

MacDorman, M. NCHS Data Brief No. 23, October 2009.

Marian F. MacDorman, PhD, CDC National Center for Health Statistics, Division of Vital Statistics, Reproductive Statistics Branch.

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