The birth rate, including unwanted births, can be traced to the level of education of women in various countries and does not correlate well with religion.
historically, increases in women's education almost immediately succeeded the availability of birth control. in more recent years, education of young women on their reproductive rights has become a factor in maintaining a low birth date. the "bible belt" and other areas that proclaim strong religious beliefs, which tend to preach abstinence-only, also have above-average teen pregnancy rates, even when the data are adjusted to exclude income factors.
Mexico, a fairly catholic country where, presumably, birth control is restricted, has a high birth rate and large family size. Education for women is also relatively restricted. (Not as bad as, say, Afghanistan, but below what is typical in oher industrialized countries).
google "mexfam" - the mexican national family planning foundation.
Italy, an even more catholic country, has one of the highest rates of women Phds in the world and generally equal opportunities for men and women (better than the US). Their birth rate is quite low and their rate of unwanted pregnancies, which is extremely difficult to measure, is seemingly much lower than ours.
i have no idea where you're getting this from. italy only fairly recently made PhD-level education available, and as such the degree is still extremely rare in the population. as with the US, roughly 50% of PhD candidates are female. for reference, about 1% of the US population holds a PhD or equivalent (excluding JD, MD, other "professional" degrees.)