By Alex Kirby BBC News Online environment correspondent

Many women have no access to contraception

It says poor countries themselves are providing over 75% of the money spent on sexual and reproductive health care.

The fund says the medical benefits of better provision are clear, with this sector causing 20% of global disease.

But UNFPA says proper funding of sexual health services would also provide many other less obvious benefits to society.

Vital for poverty battle

With the Alan Guttmacher Institute, a US charity, UNFPA has published a report, Adding It Up: The Benefits Of Sexual And Reproductive Health Care.

It is time for developed countries to live up to the pledges they made UNFPA

It says improved provision is essential if the world is to realise the Millennium Development Goals, the global commitment to a radical reduction in poverty by 2015.

The report says sexual health services mean better maternal health, the prevention of unintended pregnancies, and a reduction in sexually transmitted diseases, including HIV/Aids, which accounts for 6% of the global burden of disease.

It says: "Satisfying the unmet need for contraceptive services in developing countries would avert 52 million unintended pregnancies annually.

"This, in turn, would save more than 1.5 million lives and prevent 505,000 children from losing their mothers.

"The cost of providing contraceptive services to the 201 million women in developing countries with unmet need... would be $3.9bn per year."

Saving money

But the report says the benefits of better sexual health provision are not limited to individuals: they can mean better lives for families, and happier societies.

Geri Halliwell, UNFPA goodwill ambassador

It says: "By keeping young adults healthy and productive, by allowing parents to have smaller families... and by reducing public expenditures on education, health care and other social services, sexual and reproductive health services contribute to economic growth and equity.

"By enabling young women to delay childbearing until they have achieved education and training goals, and preventing stigmatising medical conditions, [they] contribute towards improving women's social position... "

Called to act

But the report says the developed countries are still a long way from making good the commitment they made 10 years ago, at the Cairo International Conference on Population and Development.

In 2000, it says, they provided $2.6bn for sexual and reproductive health services - less than half what they had pledged in Cairo to be committing by then.

It notes: "More than three-quarters of spending on sexual and reproductive health care is currently provided by individuals, governments and non-governmental organisations in developing countries.

"While the developing countries must continue investing... it is time for developed countries to live up to the pledges they made at the 1994 conference."