WEDNESDAY, March 18 (HealthDay News) -- The number of unmarried women who are having babies has reached a record level in the United States, and Cesarean delivery rates continue to hit new highs, a government report shows.

The total number of births, birth rate and proportion of births to unmarried women all increased by 3 percent to 5 percent from 2006 to 2007. The estimated 1,714,643 babies born to unmarried women in 2007 accounted for 39.7 percent of all births in the country.

The total number of births rose to 4,317,119 in 2007, the highest number of births ever registered in the United States. The Cesarean delivery rate increased by 2 percent, to 31.8 percent, in 2007 -- the eleventh consecutive year of increase and another record high for the nation, said the report from the National Center for Health Statistics at the U.S. Centers for Disease Control and Prevention.

Among the other findings:

• The birth rate for teens rose 1 percent between 2006 and 2007, from 41.9 to 42.5 births per 1,000 females aged 15-19.
• Birth rates for females aged 10-14 remained unchanged but increased for women in their 20s, 30s and early 40s.
• The U.S. fertility rate increased 1 percent in 2007, to 69.5 births per 1,000 females aged 15-44. That's the highest rate since 1990.
• The percentage of low birth-weight babies (less than 2,500 grams) decreased, from 8.3 percent in 2006 to 8.2 percent in 2007. Over the past few decades, low birth weight rates have steadily risen; this is the first decline since 1984.
• The rate of preterm births (babies delivered after less than 37 weeks of pregnancy) decreased 1 percent, to 12.7 percent in 2007. The decline occurred predominately among infants born late preterm (between 34 and 36 weeks). Since the early 1980s, the preterm rate in the United States has increased by more than a third.

The report is based on an analysis of nearly 99 percent of birth records reported to 50 states and the District of Columbia as part of the National Vital Statistics System.

The March of Dimes said it hopes the decline in the rate of preterm births will be the start of a new trend in improved maternal and infant health.

"We're encouraged by this drop in the preterm birth rate and hope that the emphasis we've put on the problem of late preterm birth is beginning to make a difference," president Jennifer L. Howse said in a news release about the statistics. "Through our Prematurity Campaign, we can build on this success and begin to give more babies a healthy start in life."

Preterm birth, the leading cause of newborn death, costs more than $26 billion annually, according to the Institute of Medicine. Preterm babies who survive are at risk for numerous health issues, including mental retardation and breathing problems, the March of Dimes said.

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