Transmission of Trichinella to humans is still a global public health concern. Although theoretically possible, vertical transmission of Trichinella has rarely been investigated. In June 2005 an outbreak of trichinellosis was reported in Udomxay province, the Northern Lao Peoples' Democratic Republic (PDR). In February and March 2006 we performed a study of all pregnant and lactating mothers and infants in the location of this outbreak to assess the possible occurrence of vertical transmission. The study used questionnaires, mother and child clinical examinations, and serology (Western blot) and, based on the results, women were classified as suspect, possible, or confirmed cases. A control group included unexposed pregnant women and their children. Among 200 women from 21 villages, 8 were confirmed positive for trichinellosis by serology; 4 of these were symptomatic. Among their children, one died in utero at 26 weeks gestation due to maternal hepatitis of unknown etiology and a second child had Trichinella-specific IgG antibodies but was clinically normal. A third child, with negative serology had an inter-ventricular cardiac communication. The remaining children did not differ from controls. Our results cannot prove that transmission of trichinellosis occurs from mother to child.