In a parallel universe...
Pope Paul VI would have issued this instead of Humanae Vitae:
http://www.endowonline.com/__metadot__/attachment/download/50800
It's the final report of the Pontifical Commission for the Study of Population, Family, and Births. Originally appointed by Pope John XXIII around the same time as Vatican II was wrapping up, the commission continued with Pope Paul VI's wishes that some clarity be brought to the issue of birth control.
The commission was comprised of clergy, theologians, philosophers, doctors, psychologists, sociologists, and married couples. Can you get any more comprehensive than that? For 3 years they met and debated and argued and discussed and reflected and prayed and studied and lost sleep over the issue of birth control. I would think they'd be the "expert opinion" on the matter of its morality and acceptable use.
So why did Paul VI summarily dismiss and ignore their recommendations in favor of Humanae Vitae? It's a long story. I just read "The Politics of Sex and Religion" by Robert Blair Kaiser which discusses the formation of the commission, the development of their recommendation, the 'minority report' written to refute their findings, and the final result. It's not light reading, but it is intriguing none the less.
I can only imagine where the world would be today had he followed their advice instead of the minority report. If contraception were an acceptable option in the Catholic church's eyes, how far would that go to help prevent the spread of STDs, stop unwanted pregnancies, reduce the number of abortions, fight overpopulation, and lower the number of abandoned children in orphanages or on the streets?
But perhaps I overestimate the power of the Vatican. I wonder how much sway it really has in the world these days. I spend my time arguing with ultra-conservatives so I tend to think that they are rampant throughout the population. Maybe there are less of them than I think. Someone mentioned today that 78% of US Catholics use contraception. How they arrive at that number I don't know, but it is interesting if it's true. I wonder what the statistic is in other countries. Perhaps US Catholics don't listen to the Vatican as much as other people do.
Would the world be much changed in that parallel universe? I wonder...