No, there is no evidence that rhubarb can cause contractions. In fact, it is not known to have any effects on the body's muscles or hormones in general. Rhubarb has been used for centuries as a medicinal herb due to its high content of vitamin C and other vitamins and minerals, but there is no scientific proof that it can induce labor in pregnant women or cause uterine contractions. There are many herbs available which may help promote healthy uterine contraction during pregnancy; however, they should always be taken under the advice of a physician.