Pregnant women who lie in a supine position may develop syncopal symptoms. However, of those women who become symptomatic, only 2% to 4% have significant aortocaval compression. Even in this small minority of symptomatic women, there is no evidence of fetal compromise. The advice often given to pregnant women to lie on the left side is therefore not relevant. In some women, experiencing a pre-syncopal episode will cause them to avoid lying in the supine position.