It is not advisable to engage in activities that involve excessive movement or impact during pregnancy, especially in the later stages. Jumping on a motorbike can put strain on your abdomen and potentially harm your baby. If you are experiencing pain in your tummy after this incident, it is important to seek medical attention immediately. Your healthcare provider will be able to assess the situation and determine if any further action needs to be taken. Remember, it is always better to err on the side of caution when it comes to the health and safety of both you and your baby during pregnancy.