Your employer cannot decide on your behalf what you are and are not capable of doing - they are not medical practitioners or midwives, so it is not their call to make. Their only obligation in regards your pregnancy is to listen to YOU about what YOU say you are capable of, and failing that, what a medical certificate says you are capable of. It is not their decision to make and 'compassion' is so laughable. If they were so compassionate they would have discussed keeping you on the same money so as not to create financial stress on you while you are pregnant. Compassion my arse.
They are sulking now, because you've taken it further, and most people just pull their heads back into their shells, hoping not to get their heads lopped off.
If you're going down, you're going down loud - make a noise about it, because you may as well from here on in. Give them a headache, make them spend money on legal advice, it's very satisfying
I hate power trips and people who think laws don't apply to them and their profit margins.