 The purpose of this study is to compare the efficacy of two doses of nevirapine NVP given only to the infants or lopinavirritonavir LPVr from 28 weeks gestation with single dose SD NVP given to the mothers plus two doses to the infants, in addition to zidovudine ZDV prophylaxis from 28 weeks gestation and for one week of ZDV in neonates for the prevention of mother-to-child transmission of HIV-1. 