Aria Amour Hill was born 12:17 p.m. on Oct. 23, 2011 to proud parents Natasha Gibson and Quinton Hill at Washington Hospital Center, which delivers more than 4,500 babies a year. It’s the busiest maternity ward in the District. (Linda Davidson/THE WASHINGTON POST)

The District’s infant mortality rate, long among the highest in the country, has fallen to a historic low because pregnant women are smoking less, fewer teenagers are having babies and women have better access to prenatal care, according to a Health Department report to be released Thursday.

Of 9,156 children born in the District in 2010, 73 died before their first birthday, a rate of 8 per 1,000 births, according to the latest data available.

The District’s infant mortality rate was one of the worst among large U.S. cities, peaking in 1989 at 23.1 per 1,000 births. The rate fell to 13.1 in 2007 and declined steadily for each of the following three years. Although it is still higher than the national infant mortality rate of 6.1, it is lower than rates in Baltimore (11), Richmond (13.5) and Detroit (12.8), D.C. officials said.

“It takes a lot of effort to bring it down point by point,” said Mohammad Akhter, director of the District’s Health Department. “It’s a huge, huge thing.”

Infant mortality is considered one of the key indicators of a community’s well-being. Its leading causes include birth defects, maternal complications of pregnancy, low birth weight and sudden infant death syndrome. Poverty and lack of access to health care play a large role.

Akhter said the declining rates were the result of long-term investments in support programs for vulnerable mothers and children that were expanded several years ago, under then-Mayor Adrian M. Fenty, other city leaders and community organizations.

The programs increased the number of families who receive parenting help and other assistance from a city-run home-visit program.

A large part of the declining infant mortality rate can be attributed to extra home visits in high-poverty areas of the District: wards 7 and 8. In three years, the number of home health visits to wards 7 and 8 nearly doubled, from 4,392 in 2007, to 8,712 in 2010, data show.

Using information from birth certificates, Health Department staff members visit mothers who have had children who died or were born with birth defects to offer assistance for future pregnancies, he said.

That includes connecting them to medical care or other social services.

In addition, the health of high-risk women and children has been improved by better access to primary care clinics in all city wards and better health coverage through the D.C. Healthcare Alliance, the city insurance program for low-income residents who are ineligible for other public assistance.

“This is very good news for the District of Columbia,” Mayor Vincent C. Gray (D) said in a statement. The data tell “us that the public health programs in the District are working and working well. Long-term investments, particularly in wards 7 and 8, are proving to have a direct impact with the District’s most vulnerable populations.”

Smoking, one of the leading causes of low birth weight and premature births, has fallen among pregnant women. Teen pregnancies have also dropped, from 1,114 in 2008 to 967 in 2010. The proportion of births to teens 15 to 19 decreased by 9.3 percent from 2009 to 2010, data show.

Another key factor, city officials said, has been outreach efforts to increase early prenatal care, particularly for black and Hispanic mothers.

Women who receive late or no prenatal care are at risk of having undetected pregnancy complications that can be fatal for them or for their babies.

The overall reduction in the infant mortality rate was driven in large part by to a drop in the deaths of infants born to black mothers; that rate fell from 14.2 in 2009 to 10.7 in 2010, data show. The infant mortality rate for Hispanic mothers fell from 8 in 2009 to 3.7 in 2010.

Research editor Alice Crites contributed to this report.