It's not like they're not being fruitful and multiplying (I'd say they are exponentiating), after all, and the spilling seed thing would only prohibit condoms. Also, since abortions apparently delay the coming of the Mashiach or something or other, surely birth control can be justified on those grounds.
Of course, the Efrat people may just be making things up
"Since the beginning of the financial crisis there has been an increase in the number of women opting for abortions, including religious and haredi women who can't bear the costs of raising another child," said Rabbi Dr. Eliyahu Schussheim, chairman of the Efrat foundation for the prevention of abortions.
I guess on the plus side, the Efrat foundation seems to focus on an individual level rather than a legal one.