Borderline Low Free T4

At yesterday's 6 week appointment I got an ultrasound and blood work. My doctor's office just called and said my T4 was borderline low (80), and that I'll have to have my thyroid tested when I go in at 8 weeks. Of course I Googled this, and if left untreated could lead to miscarriage, preclampsia, still born, low birth weight, etc. Just curious if anyone else experienced this and was fine? I had my TSH tested back in December and that was normal (2.17), which I think TSH is more of an indicator of hypothyroidism. My doc back in December said I didn't have a thyroid problem