Unfortunately, the data not only don't back them up - they actually show these people up as hypocrites. Just earlier this month, one of the most detailed, multinational studies ever undertaken was published in The Lancet. The study, a collaboration between scientists from the World Health Organization in Geneva and the Alan Guttmacher Institute in New York, used epidemiological techniques to reveal the rates of all abortion - legal and illegal - in countries around the world.
The study found that legalising abortion has no effect on the number of abortions. The only effect of illegalising abortion is to make it more dangerous for the mother. In fact, Western Europe, where abortion is mostly legal, has the lowest rates of abortion in the world! The authors say:
The abortion rate per 1000 women was lowest in western Europe (12), and was also quite low in northern and southern Europe (17–18) and Oceania (17). In these geographic areas, most abortions were legal and abortion incidence had been low for decades.
So why was the official rate in the UK so low in 1968? It's because in the first years after the law was passed, most abortions were still conducted illegally, and so don't show up in the official statistics.
So why are abortion rates so low in Western Europe? The Lancet study answers that one too. It backs up numerous other studies which show that the best way to reduce abortion rates is to provide easy access to contraception. If religious groups were really interested in reducing abortion, they would be out there handing out condoms!
In other words, these religious groups are hypocrites, and dangerous ones at that - they are campaigning to increase abortion rates and maternal death rates - and all because of their wretched, dark age dogma!
Ref: Sedgh G. Induced abortion: estimated rates and trends worldwide. The Lancet 2007; 370:1338-1345.