Hypothyroid and pituitary during pregnancy

I have secondary hypothyroidism due to my pituitary and I'm wondering if this can affect fetal brain development the same way as primary hypo even though I have normal tsh . (but t4 is low) i believe I was undiagnosed during pregnancy because of my normal tsh. Now postpartum looking back at my symptoms I think I would of  devolved it after the 12 week mark where the fetuses thyroid "mostly" takes over. Thankyou I'm just worried about my baby