Two hundred five consecutive cases of noncatastrophic trauma occurring during the second half of pregnancy were evaluated prospectively. Pregnancy complications as a result of trauma occurred in 18 of 205 patients (8.8%): premature labor (n = 10), placental separation (n = 5), fetal injury (n = 1), and fetal death (n = 2). Multiple regression analysis of the data base showed obstetric findings (contractions, uterine tenderness, and bleeding) on presentation to be highly associated with complications (17/88; 19.3%). In their absence complications were rare (1/117; 0.9%). Detectable fetomaternal hemorrhage was significantly more common in trauma patients (18/205) than in control subjects (2/110) (p less than 0.01), but its role in managing trauma patients was limited to detection of rare massive hemorrhage (1/205) and detection of rare hemorrhage exceeding that covered by the standard Rho (D) immune globulin dose (2/205). Fetomaternal hemorrhage need not be quantitated in patients who lack obstetric findings on presentation. Despite rare reports of delayed abruptio placentae, it is doubtful that prolonged observation (greater than 2 to 3 hours) in the hospital is necessary in patients who lack obstetric findings on initial presentation.