In a recent BBC interview, Gates has said she is “optimistic” that the Catholic Church will change church teaching on contraception in order to help women in developing countries.

“We work very extensively with the Catholic Church and I’ve had many discussions with them because we have a shared mission around social justice and anti-poverty,” Gates said.

“And I think what this Pope sees is that if you’re going to lift people out of poverty, you have to do the right thing for women,” she said, even though “we have agreed at this point to disagree” on contraception.

Her comments come as her charity, the Bill and Melinda Gates Foundation, is currently co-hosting an international summit in London on the issue of access to contraception in the developing world.

But such change is impossible, said John Grabowski, associate professor of moral theology and ethics at Catholic University of America.

“The Church’s teaching on opposing contraception isn’t a recent teaching, it’s not something made up by Pope Paul VI in 1968,” he told CNA.

In 1968, Pope Paul VI wrote Humanae Vitae, an encyclical “on the regulation of birth” that spells out Church teaching on family planning and contraception as it applies to the modern world.

This teaching is also articulated in the Catechism of the Catholic Church, which states in paragraph 2370 that contraception implies “not giving oneself totally to the other. This leads not only to a positive refusal to be open to life but also to a falsification of the inner truth of conjugal love, which is called upon to give itself in personal totality...The difference, both anthropological and moral, between contraception and recourse to the rhythm of the cycle...involves in the final analysis two irreconcilable concepts of the human person and of human sexuality.”

But the 1960s was not the first nor the only time the Church has affirmed that the marital act has inseparable unitive and procreative meaning, Grabowski said.

“This has been the teaching of the Church from its beginning, so the Church (including Pope Francis) can’t change constant, universal, authoritative teaching.”

Furthermore, Grabowski added, “Pope Francis has shown no indication that he wants to. He’s been absolutely emphatic in reaffirming the teaching of the Church in this area.”

In his encyclical Amoris Laetitia, Pope Francis said that: “From the outset, love refuses every impulse to close in on itself; it is open to a fruitfulness that draws it beyond itself. Hence no genital act of husband and wife can refuse this meaning, even when for various reasons it may not always in fact beget a new life.”

One of his predecessors, Pope John Paul II, also taught extensively that contraception is not only a violation of natural law, but of sexuality and marriage as revealed to humanity through Scripture, Grabowski noted.

“So if this is a truth entrusted to the Church in revelation, then the Church has no authority to change it,” he said.

Moreover, scientific data does little to prove that contraception is truly what’s “right for women” as Gates has said, Grabowski added.

“I’d start with physical health - even current low-dose oral contraceptives are a Class 1 carcinogen, they significantly raise women’s chances of suffering from heart attack, stroke, pulmonary embolism. There’s all kinds of health risksassociated with most contraceptives,” he said.

“So, good for women? The data doesn’t support that,” he said.

Instead of contraception, the Church proposes various methods of fertility awareness, or Natural Family Planning, to help families plan their children in such a way that does not separate the procreative and unitive aspects of sex.

While these methods have been effective in developing countries where it is taught and promoted well, the Church could do yet more to support people who want to follow Church teaching, Grabowski noted.

“Could the Church doing a better job of talking about these methods of fertility awareness and their benefit? Absolutely,” he said.

“We’ve got a culture that is promoting and empowering contraception and the Church (needs to) articulate a clear enough alternative with a vision and how we can realize it.”