Wanting - that sounds to me like really dodgy science from your midwife there, though I could be mistaken.
Don't get me wrong, I'm not judging (i have happily eaten medium- rare steak in pregnancy as I feel the toxoplasmosis risk from steak is minute) but the difference between eating it before 12 weeks and after 12 weeks makes little sense, from what I've read.
Was your midwife arguing that after 12 weeks you're less likely to contract toxo even if the meat is infected, because your immune system is stronger?
Or was she arguing that, after 12 weeks, if the meat was infected it would cause less damage to the baby?
Because from my reading on toxoplasmosis (again, something you're much more likely to get from your garden than from steak!), it is more likely, not less, that an infected pregnant woman will pass the infection to her baby in later pregnancy, compared to the first trimester.
The difference is that, in the first trimester, the infection would be more likely to cause miscarriage whereas later on it would be more likely cause birth defects, rather than ending the pregnancy.
Would be really interested to hear if your midwife has new/updated information.