Dozens of teen pregnancy prevention programs deemed ineffective by President Donald Trump's administration will lose more than $200 million in funding following a surprise decision to end five-year grants after only three years.

The administration's assessment is in sharp contrast with that of the American Congress of Obstetricians and Gynecologists, which credited the program with contributing to an all-time low rate of teen pregnancies.

Rachel Fey of the National Campaign to Prevent Teen and Unplanned Pregnancy said Tuesday that grantees under the Teen Pregnancy Prevention Program were given no explanation when notified this month their awards will end next June. The program, begun under President Barack Obama's administration, receives about $100 million a year.

"We know so little about the rationale behind cutting short these grants," said Fey, who said the teen birth rate has fallen by about 40 percent nationally since the program went into effect in 2010. The focus of the program is on evidence-based interventions aimed at preventing teen pregnancy. It does not pay for or provide contraceptives.

A Health and Human Services spokesman said late Tuesday that an evaluation of the first round of grants released last fall found only four of 37 programs studied showed lasting positive impacts. Most of the other programs had no effect or were harmful, the department said, including three that it said increased the likelihood that teens would have unprotected sex and become pregnant.

"Given the very weak evidence of positive impact of these programs, the Trump administration, in its ... 2018 budget proposal, did not recommend continued funding for the TPP program," the department statement said.

The American Congress of Obstetricians and Gynecologists urged the administration "not to turn back the clock" on progress.

"It's as though the evidence and the facts don't matter," ACOG President Dr. Haywood Brown said.

The North Texas Alliance to Reduce Unintended Pregnancy in Teens, one of more than 80 current grantees around the country, will lose just under $1 million a year, about three-quarters of its budget, Executive Director Terry Goltz Greenberg said. The program worked with more than 1,700 kids last year in high-poverty neighbourhoods where the teen birth rates are three to five times the national average, she said.

"Most of the evidence-based programs are not just talking about contraception but are putting it in the context of bigger goals in life, such as, 'Where do you want to be in three years?' 'How does a kid fit into that,"' she said.

Elizabeth Gomez, 44, said the Texas program's after-school classes taught her how to discuss difficult topics with her three daughters in a respectful way that made them listen and respond.

"For Hispanics, it's difficult, because it's a taboo to talk about sex," she said.

A letter to Health and Human Services Secretary Tom Price signed by 37 Democratic senators called the decision short-sighted. Teen Pregnancy Prevention Program grantees served a half-million youth from 2010 to 2014 and were on their way to serve an additional 1.2 million through 2019 when the grant was scheduled to end, the senators said. Their letter asked Price for an explanation and questioned the timing of the notifications in advance of congressional action on fiscal year 2018 appropriations.

Two of Shawanda Brown-Cannon's children take classes once a week through a southwest Georgia program called Quest for Change which, according to its director, will lose about 87 percent of its total budget.

The classes prompted both her 17-year-old daughter, Amaya, and her 13-year-old son, Chandler, to talk with their mother about what they've learned, for instance a Valentine's Day class on how to show love without sexual activity.

"It opens up a line of communication," Brown-Cannon said.

Angelina Jackson, a 17-year-old high school senior, is a member of Quest for Change. She helps run classroom lessons and organise events as a member of the youth leadership council focused on her school.

"Some people are not able to talk to their parents at home about the stuff that Quest does," Jackson said. "They provided a comfortable environment where people could ask questions or talk about their concerns."

Vermont-based Youth Catalytics was informed July 5 that its five-year, $2.8 million federal grant had been cut off June 30, the end of the first year. The grant provided about half of the organisation's annual budget. As recently as July 3, people from the organisation had been working with HHS officials about the details of the program, said Meagan Downey, the group's director of special projects. The grant covered about half of her salary.

Downey said her organisation was one of five grant recipients nationwide that lost their funding immediately. Others were given until July 1, 2018 to prepare for the loss of the funds.

Leaders of the HOPE Buffalo program always had an eye toward establishing partnerships with city and community leaders that would enable its work to continue beyond the five-year lifespan of the grant, which provided $2 million a year, Project Director Stan Martin said. With less time and less funding, he said, "our efforts were just accelerated."