The changes in left atrial (LA) size and function during normotensive and preeclamptic (PE) pregnancy have rarely been previously studied and the results have been inconsistent. The aim of this study was to assess the time changes in LA volume during normal pregnancy, to determine the impact of the increased afterload occurring in PE on maternal LA, and to compare differences in LA geometry and function between early-onset and late-onset PE. Using a real time three-dimensional echocardiograph, the body surface area-indexed LA volume and emptying function (EF) were compared between nonpregnant controls (n = 30), normotensive (n = 43), and PE (36 with early-onset PE and 34 with late-onset PE) pregnant women. During normotensive pregnancy, the indexed LA maximum, pre-contraction, and minimum volumes progressively increased, as well as total, passive, and active EF (P < 0.05, Trimester 3 vs. controls), as an adaption to risen cardiac preload. In the PE group, indexed LA volumes were significantly enlarged and the values of LA EF were markedly decreased (P < 0.05) resulting from elevated ventricular filling pressure and diastolic dysfunction. Compared with late-onset PE, smaller LA volume and greater atrial EF were shown in early-onset PE despite a higher afterload and more hypertrophied ventricle. In conclusion, LA size and function gradually improved to maintain adequate blood volume during normotensive pregnancy, while dilated chamber and reduced action of LA occurred in PE associated with increased afterload. Less LA volume and higher LA EF were shown in early-onset PE than in late-onset PE.