Hi, thanks for posting your concern in the HCM. The medicine you mentioned is a uterine relaxant used to prevent uterine contraction and premature labour.It is safe in pregnancy. However,it can cause increased maternal heart rate. Back pain is quite common in pregnancy. You should avoid constipation and maintaining fixed posture or prolonged sitting to avoid worsening of back pain. Ispagulah husk 2 tsf in cup of water at bedtime and high fiber diet would help you avoid constipation. After the first trimester, you may also start pregnancy exercises after proper training from your Obstetrician, which would also help you. Thirdly, preferably you should lie down in left lateral position. This will help in blood circulation and also avoid stress to paraspinal muscles. Please avoid any analgesic. You should also have a routine urine examination, because UTI is very common in pregnancy and may cause back pain too. For any further questions, please write back. Regards, Dr. Kaushik