Simple low free thyroxine in pregnant women does not require special treatment, and regular monitoring of thyroid function is recommended. If it is accompanied by high thyrotropin, combined hypothyroidism in pregnancy should be considered. 1. Simple low free thyroxine: Simple low free thyroxine with normal thyrotropin can be treated by consuming iodized salt and closely monitoring thyroid hormones. 2. Low free thyroxine accompanied by high thyrotropin: This indicates that the body’s demand for thyroid hormones has increased. In order to ensure the growth and development of the fetus, thyroid hormone replacement therapy should be carried out to maintain the thyroid function within the normal range. If low free thyroxine is detected during pregnancy, you should consult a doctor for timely treatment.