birth control (last time I heard) causes early abortions. Plus it messes w/ a woman's natural menstrual cycle and causes health problems like blood clots.
on top of that, the Original Church has always taught it is immoral. It sends a message to all society that sex can be for pleasure alone. That last sentence is from yours truly and not necessarily what the Catholic Church teaches, although I am sure what I just said is PART of the reason the Church is against it. Also, I don't speak for the novus ordo Church run by Francis. I have left that fake Church for the real Catholic Church, the Society of St Pius X (too bad we true Catholics can't just say Catholic Church anymore without some lengthy explanation of what tht means but.. it is what it is)
In any case, women should love themselves a little more.. abstain from ANY sex whatsoever until a man proves he is serious, namely by talking about a life time commitment