Twelve pregnant women and one woman who had just given birth were hospitalized with measles in Houston between 1988 and 1990. The most common and serious maternal complication was pneumonitis (seven patients). Other maternal complications included hepatitis (seven patients), premature labor (four patients), spontaneous abortion (one patient), and death (one patient). For four of 13 patients, all of whom had severe measles and pneumonitis due to measles virus, an adverse fetal outcome such as abortion or prematurity was associated with their conditions. Historical accounts describing maternal sequelae of measles have suggested more severe disease in pregnant women, although this observation has not always been confirmed by more recent reports in developed countries. The clinical course in our patients suggests that measles during pregnancy may be associated with serious complications.