WASHINGTON – Maine, which had one of the highest teen pregnancy rates in the nation 25 years ago, now has one of the nation’s lowest teen birth rates.

Maine’s 15- to 19-year-olds had 29.8 births per 1,000 in 1999, compared with 43.5 per 1,000 in 1991, according to a report released Tuesday by the National Center for Health Statistics.

Only Massachusetts, Vermont and North Dakota have lower rates.

State health officials attributed the sharp decline in the 1990s to an increase in sex education programs.

“Abstinence-based comprehensive family life education has become the standard in most school systems in Maine,” said Dr. Dora Mills, director of Maine’s Bureau of Health. “In other words, we’re teaching our youth that abstinence is the way to avoid pregnancy and sexually transmitted diseases and other issues.”

Mills also cited improved access to reproductive health care as leading to the decline. That does not necessarily mean abortion services, she said, noting that the teen abortion rate has declined in Maine in recent years.

Maine’s decline is in keeping with national trends. The birth rate for teen mothers fell 3 percent nationally in 1999. The rate has fallen 20 percent since 1991 and is now at a record low.

The previous low teen birth rate, recorded in 1986, was 50.2 births per 1,000 teen-age women. The records go back to 1940.

The report also showed that 89.2 percent of mothers in Maine begin prenatal care in the first trimester. Only Connecticut, Massachusetts, Rhode Island and New Hampshire have higher percentages, the report said. It also found 6 percent of babies born in Maine have low birth weights, the eighth-lowest percentage in the country.