The city’s birth rate hit a 25-year low in 2005, even as Mayor Bloomberg is projecting a population spike of 1 million people by the year 2030.

The city’s newest release of vital statistics — an annual compendium of deaths, births, disease, and accidents — shows that 122,725 babies were born in New York City in 2005, or 1,374 fewer than in 2004.

City health officials say the birth rate, a tally of the number of births per 1,000 people, dropped nearly 8% in the last decade and mirrors the national trend toward smaller families started later in life.

“Families are having fewer children,” the deputy commissioner for epidemiology at the Department of Health and Mental Hygiene, Lorna Thorpe, said. “That is a nationwide trend and we’re seeing it here in New York City.”

The health department is also attributing the drop to the dramatic decline in the number of girls younger than age 20 having babies. In 1992, teenage girls had 13,795 of the 136,002 babies born in the city, while in 2005 they had 8,579 of the 122,725 born. In other words, the overall births declined, but teen births declined more steeply.

The city’s population forecasters say that even with the birth rates, which have steadily declined since peaking in 1990, the number of people living in the city is still expected to soar over the next two and a half decades.

Some of that is simply because there are still more than double the number of babies being born each year than people dying. And, the New Yorkers who already have been born are living longer than they have at any point in the city’s recorded history.

The average life expectancy for New Yorkers in 2004 increased to 78.6 years, which city officials say is an all-time high and an almost 10 month increase over the life expectancy age in the city in 2001. The life expectancy in the city was higher than the national average of 77.9 years.

The fact that people are living longer in the city is one of Mr. Bloomberg’s favorite statistics to boast about when he is ticking off the positive indicators the city has seen on his watch, including a decrease in crime.

The city logged fewer deaths in 2005 — 57,068 to be exact — than in more than 100 years. There were slight declines in the three leading causes of death (heart disease, cancer, and pneumonia), but diabetes deaths increased by 5% and more people died of Alzheimer’s disease. The city also experienced a drop in the number of smoking related deaths, coinciding with an aggressive anti-tobacco campaign.

The deputy director of the population division at the Department of City Planning, Peter Lobo, said the city is expecting a decline in the number of school age children by 2020 because of the fertility declines. But he cited a report, released last week by his office, estimating that the number of people ages 65 and older will jump by more than 44% by 2030.

The net effect of the birth, death, and migration, will mean 1 million more people, or a population of 9.1 million, by 2030, Mr. Lobo said.

The annual statistics released yesterday offer a unique glimpse into life and death in New York. They chronicle everything from marriage (which was up) to infant mortality (which was down) to baby names. They also offer breakdowns in a dizzying number of categories, including age, sex, race, borough, and neighborhood.

In 2005, there were 66,348 marriages, an increase of 4,291 weddings from the year before. Also, 380 people were killed in car accidents, 481 committed suicide, and 579 died in homicides. The most popular baby name for a girl was Emily for the third consecutive year.

Although vital statistics tend to move gradually because they are documented annually, the slight shift of diseases do offer insights into the public health priorities of Mr. Bloomberg and his health commissioner, Dr. Thomas Frieden.

Dr. Frieden, who is widely viewed as one of the most aggressive public health officials in the country, has launched a campaign against diabetes and heart disease and has upped the number of condoms being distributed as a way to further decrease rates of HIV and AIDS. The New York Sun reported earlier this week that the city’s distribution of free condoms had increased to 1.5 million a month from 250,000 a month over the past 18 months.

Dr. Frieden recently shepherded a ban on trans fats for city restaurants through the Board of Health, arguing that their artery clogging qualities make them dangerous. That came four years after he and Mr. Bloomberg won the citywide smoking ban in bars and restaurants.

Meanwhile, while the birth rate declined citywide, it was up in the Boro Park section of Brooklyn, a predominately Chasidic neighborhood where the families have more children than average. Maimonides Medical Center in Boro Park was the hospital that saw the most births in the city, 6,709. No other hospital cleared 6,000. The birth rate was also up in Lower Manhattan, which is seeing an increasing number of residential towers and an influx of new TriBeCa residents.

And, while the teen birth rates were down overall, they are still far higher among Hispanic girls and were highest in the Bronx. The city has ramped up outreach to teens in lower-income areas to educate them about unwanted pregnancy.

The number of reported abortions in the city was down to a low in the past 10 years, to 88,891 in 2005 from 91,673 in 2004.

Of the city’s births in 2005, 52% of them were paid for by Medicaid, the government health program for the poor. Of women giving birth in New York City, 44% were unmarried.

The full vital statistics report is available on the Health Department’s Web site, which is reachable via nyc.gov.