Objectives: The objectives of this study were to estimate dengue seroprevalence in a population of Thai pregnant women, living in a highly endemic area and placental transfer of dengue antibodies.
Methods: A cross-sectional seroprevalence study of 245 pregnant women at delivery.
Results: Dengue HAI antibodies were positive in 94.7%. Maternal age was the only risk factor associated with dengue infection as older mothers (>20 years) were significantly more likely to be seropositive than younger women (p<0.0001). Cord antibody titres varied with maternal age and antibody titre, were significantly higher in babies born to younger mothers (<20 years) (p=0.01), and were significantly correlated with maternal titre. Low birthweight babies had lower transfer ratios for DEN-2 antibody (1.06) compared to heavier babies (1.36, p=0.05). No mother or neonate had dengue IgM detected. Two women were classified as recently, but not currently infected with dengue virus and we consider it likely these were first trimester infections. As no infant became infected the fetal infection was 0%.
Conclusions: Younger mothers were more likely to have been recently infected, resulting in higher antibody titres. Maternal dengue antibody transfer was proportional to maternal antibody concentration.