Family planning helps people in Africa to be healthier and wealthier, as women without contraceptives become locked in "a cycle of poverty," Melinda Gates told AFP as a conference on the topic was held in Ivory Coast.
"When a woman has access to contraceptives she can lift herself out of poverty, and if she doesn't have access to contraceptives, it locks her inside a cycle of poverty for the rest of her life," said the wife of Microsoft co-founder and billionaire Bill Gates, whose foundation is very active in the field.
Family planning has "huge health benefits for the woman and for her children, and it has economic benefits," Gates told AFP by telephone from the Ivorian economic capital Abidjan during the fifth annual meeting of a West African partnership on the topic.
Experts from nine countries met in Abidjan with technical and financial backers in the Ouagadougou Partnership, which aims to bring family planning to 2.2 million more people across the region by 2020.
"If (a woman) has less children and can space them, she is less likely to die. Her children grow up healthier and the family is wealthier," said Melinda Gates.
"Family planning is absolutely part and parcel of economic development, just like agriculture and education," she added, stressing that "it's imperative that it's voluntary.
"The woman has to be educated about it and decide if she wants to use it. There are examples all over the world. If you coerce people, that is not a thing to do... China has backed away from its policy.
"One thing you see more and more African countries talk about is the 'demographic dividend'. They know they want to bring down their maternal mortality rate, they know it will help lift people out of poverty and ultimately increase their GDP (gross domestic product)."
The Ouagadougou Partnership acknowledges that the goal of 2.2 million women in five years "may seem low", but argues on its website that the target is "in reality very ambitious" in light of limited funds, socio-cultural barriers, a low contraceptive prevalence rate and "timid political commitment."
Gates is more upbeat, since an initial target of one million women has already been exceeded. In her eyes, ongoing success depends on educating "the power structures -- husband and faith leaders -- around the women, and then you talk to the women."
"I've been to dusty villages in remote places in Niger and talked to women who know about family planning and are using it. I said, 'I'm skeptical. How is the word going to get out?'
"'We're getting the word out,'" women replied. "'We meet. We meet at the well, when we grind millet, when a new baby is born. We know we're not getting enough water, it's not raining as much, we're not getting much off our farms. We want to have less children ... and we're educating our sisters'."
Religious leaders in Muslim communities have accepted that "family planning is allowed even in the Koran," said the co-founder of the Bill & Melinda Gates Foundation.
"When you meet with faith leaders, they will tell you they know a mother, a sister, a wife that died in childbirth. They know it's better for women to use contraceptives, so you have to start there."
In Niger, one of the world's poorest countries with the highest global birthrate at 7.6 babies per woman, schools for husbands have started and men have begun to understand that the best option for their children to survive into adulthood is to have fewer of them, rather than more.
"When family sizes come down... and they're only feeding two children so they've got more income on what comes out of their farm," Gates said.
Such families set a compelling example, but medical follow-up is vital. Gates met a woman in Niger with a tiny plot of land and six children to raise while her husband was off looking for work.
"I can't have more children. Can't you see that this is a life-and-death emergency for me?" Gates quoted the woman as saying, but no contraceptives were available.
"The governments have to fix the supply chain and make sure women have access," she said.