While there's no consensus on avoiding water parks and amusement rides while you're pregnant, you may want to check with your care provider before riding a roller coaster or going down a rapid water ride. Research indicates that trauma during pregnancy that produces a forceful shearing effect - such as the sudden stop experienced in a car crash - can cause the placenta to separate from the uterus (placental abruption). Placental abruption can seriously complicate your pregnancy. This type of force may be experienced to a lesser extent in an amusement ride.
Many themepark rides have restrictions for pregnant women. If you decide to go on a ride, be sure to check the restriction policy first. Bottom line: You may want to stay on the safe side and stick with lounging in the pool rather than flying down a wild ride during the months you're pregnant.