90mcg is not even ONE TENTH of a SINGLE mg. This amount is completely arbitrary and does not need to be considered while talking about total dosage. It's no where near enough for pregnancy, it's quite a crime.
I can't advise you on dosage, but if my wife was pregnant, she'd be getting at least one iodoral a day.. or perhaps even one in the morning and one in the evening.
But I'm not familiar with what mega dosing during pregnancy would do (>100mg a day).