Hello dear, I understand your concern. In my opinion the ride can also sometimes cause miscarriage. Any physical strain,intercourse are must be avoided in the first trimester ie.,upto 12 weeks of pregnancy. You need to be careful in pregnancy but extra careful during the initial months. The miscarriage presents with pain abdomen,spotting or bleeding.In that case consult your doctor. If you do not have such complaints there is no chance of miscarriage. But take care to avoid such activities and take good rest. Take healthy nutritional diet and adequate fluids upto 3 litres per day. Hope this helps. Best regards...Dr.Srilatha