The Church pays great attention to the distress of infertile couples, she cares for them and for this very reason encourages medical research. Science, however, is not always able to respond positively to the desires of numerous couples. I would therefore like to remind spouses in a condition of infertility, that this does not thwart their matrimonial vocation. Spouses are always called by their baptismal and matrimonial vocation itself to cooperate with God in the creation of a new human life. The vocation to love is in fact a vocation to the gift of self, and this is a possibility that no physical condition can prevent. Therefore, whenever science finds no answer, the answer that gives light comes from Christ. — Benedict XVI, 25 February 2012.
News report with video on this here: http://www.romereports.com/palio/benedict-xvi-meets-with-the-pontifical-academy-for-life-in-the-vatican-english-6160.html