Primary HIV-1 infection during pregnancy: high rate of HIV-1 MTCT in a cohort of patients in southern Brazil by Santos Breno Riegel, Moreira Ana Maria, Campello Claudio, Canti Ivete, Turella Maria Lourdes, Lira Rita, Fonseca Rosana, Varella Ivana, Melo Marineide, Nielsen-Saines Karin