Maternity leave with some sort of pay is 9 months - but your job has to hold your position, or one comparable, for one year. If you don't return in one year they have no obligation to allow you back.
I will likely not endear myself to many people by saying this but I think Michael Moore is a crackpot hothead who only shows what he thinks will get him the publicity -and he does a good job of it. He doesn't mention waiting times at all, and in the UK they are atrocious in relation to the US. It is suggested that women get pap smears once every 3 years in the UK as opposed to once a year in the US. Preventative measures are not the same and, in my opinion, much better than in the US.
I would never, and I say this as a pregnant women in the UK having a baby on the NHS because I just can't stomach paying $22,000 for a private hospital birth, move here for the sole purpose of healthcare. I never had a problem in the US, ever, and always got the best treatments and best care.
And saying all that, I read an article that made a good point - if Moore had health problems with that big waistline of his, where do you think he would go for help? Cuba or the Mayo Clinic? I can bet it won't be Cuba.