Spending $25 per woman per year on full sexual health services would dramatically reduce mother and baby deaths and give women the choice of smaller, healthier and more productive families, according to a UN report on Thursday.

The report, by the United Nations Population Fund UNFPA and the Guttmacher Institute, described "a staggering lack of basic sexual and reproductive health services in developing countries" which means 225 million women who want to avoid pregnancy don't have access to modern contraceptives to help them.

It also found that tens of millions of women do not receive the basic pregnancy and delivery care needed to protect their own and their babies' health.

Babatunde Osotimehin, UNFPA'S executive director, urged all governments to put women's right to choose how many children to have and when at the heart of national health services.

"We know what to do and we know how to do it," he told a briefing in London. "These investments save lives, empower women and girls, strengthen health systems and have a profound and lasting impact on development."

Analysing data from Africa, Asia, and Latin America and the Caribbean, the report said it would cost on average $25 per woman aged between 15 and 49 -- roughly double the current level of spending -- to provide essential sexual health services to all women in developing countries each year.

These include contraception advice and services, pregnancy and newborn care, HIV care including medicines to help prevent mother-to-child transmission of the virus, and

treatments for four other sexually transmitted infections.

Providing these to all women who need them in developing countries would have a dramatic impact, it said -- cutting unintended pregnancies by 70 percent, unsafe abortions by 74 percent, dramatically reducing maternal and newborn deaths and virtually eliminating mother-to-baby HIV transmission.

"This is an affordable goal that will have a dramatic impact," said Ann Starrs, CEO of the Guttmacher Institute.

While the report was loaded with numbers, she said it was critical "to keep in mind the people behind the statistics".

"That includes adolescent girls, married or not, who know that pregnancy right now will mean the end of their schooling and, very likely, the end of their dreams for a better life.

"And women who have already four, five or six children and know that they cannot afford to bear and raise another one."