You are carrying 18th wk of pregnancy
with H/O 2 abortions. So need to be more careful in this pregnancy.
Although first trimester is highly risky period for miscarriage
,it can be occurred in 2nd trimester also due to anatomical defect/infection etc but chance is minimal.
At 20wk of pregnancy up and down stair is low risk but better to avoid or limited to 1-2 times daily. Use lift or escalator if available. Also avoid long journey or stepping uneven surface for at least 2 months.
Do periodic check up with USG scan for evaluation of feto placental well being. Take adequate rest and healthy diet rich in protein with iron & calcium supplements
. Be well.