When the trial began, there were limited
safety data on tenofovir in pregnancy, and randomization to tenofovir-based ART was limited
to women coinfected with HIV and HBV, because
benefit was felt to outweigh risk in that group;
comparative analyses including the group assigned to tenofovir-based ART were to be limited
to a nested HBV substudy. During period 1 (April
2011 through September 2012), women without
HBV coinfection were assigned only to zidovudine alone or zidovudine-based ART. However,
in October 2012, with increased data on tenofovirin pregnancy, the protocol was modified to allow
women regardless of HBV status to be assigned
to any of the three regimens, with an analytic
plan to compare safety across all three groups
for participants enrolled during period 2 (October 2012 through October 1, 2014)