Wecome to HCM,
Havin hypothyroid in pregnancy needs special care ,hence you should take care to keep thyroid function almost normal.
Your treating doctor will be best person to answer this but some times this is used if BP of patient is high like in Pre Eclampsia
and even in clinical anxiety.
As such is only amino acid no need to worry and we get it from our diet veg and non veg both.
You can see your Gynaecologist and Endocrinologist
to take care of your health.
If you have question you can always take Second opinion
Good Luck to you.