thanks for your query.
, ideally TSH
is supposed to be at less than 2.5.
Above this level, there are always theoretical risks such as the one you describe.
However, 6 is a borderline high value, and at this value, there is nothing much to worry about, provided you have increased the dosage.
Ideally, during pregnancy, try and keep levels to less than 3.
Some countries accept even 5 as normal, so please do not stress
Stress would damage more than other factors.