The actual thyroid hormones, Free T3 and Free T4 are more important than the TSH value. Get those tested and make sure they are well up in the ranges, before becoming pregnant again, then be sure to test them every month of the pregnancy.
Free T4 should be kept about the middle of the range and Free T3 should be in the upper half to upper third of its range.
Check your Free T3, Free T4 and TSH and type here the results along with given lab reference range.
Generally TSH is made to contain inside .3 to 3 with help of levothyroxine medicine. This is especially needed during pregnancy period as low thyroid hormones can cause either complications as you had before or baby can born with birth defects. So to avoid all those thyroid replacement treatment is started right away.
Also get checked for these too Vitamin B12, D etc. Folate and Ferritin omitted as these are usually supplemented by gyno during pregnancy period.