To date, there are no studies researching the safety of roller coasters during pregnancy. They are generally recommended to be avoided due to the jerking motions, high accelerations, and sudden stops. This increases the risk of placental abruption 1 , where the placenta separates from the uterus and poses a serious risk to you and your baby. A placental abruption prevents oxygen and nutrients from getting to the fetus and places the pregnant person at risk of hemorrhage.
If you still want to participate at an amusement park, slow-moving rides like a Ferris Wheel or train ride are better options. Always discuss with your individual healthcare provider which rides you can participate in and which are best to avoid.