What is the name of the birth control that the female characters would use?

I don't believe we're given the name of the borth control, although we are told how it was carried.

And round her waist she wore a silver-mounted green morocco-surrogate cartridge belt, bulging (for Lenina was not a freemartin) with the regulation supply of contraceptives.

"The discoveries of Pfitzner and Kawaguchi were at last made use of. An intensive propaganda against viviparous reproduction ."

"Perfect!" cried Fanny enthusiastically. She could never resist Lenina’s charm for long. "And what a perfectly sweet Malthusian belt!"