The hypothesis of PHPT-2 was that adding nevirapine (NVP) to zidovudine (ZDV) during labor and delivery, when the risk of transmission is highest, may significantly reduce intrapartum transmission without adding significant cost or logistical complications. The study used 3 arms, first arm studied zidovudine + nevirapine for mother and child, the second arm was identical but used a placebo rather than nevirapine for the child and the reference arm was the most effective zidovudine course from PHPT-1.
After the first interim analysis of this study, the zidovudine group was discontinued because the rates were significantly higher than those of the other two groups. The result of the study proved that administration of zidovudine + nevirapine to mother and infant can reduce the intrapartum transmission rate to 2%.
After the results of the study, the World Health Organisation (WHO) and the Thai Ministry of Public Health (MOPH) modified their guidelines to recommend the zidovudine and nevirapine regimen to pregnant women and their infants. Guidelines also recommend that women who need treatment for their own health receive more potent anti-retroviral combinations as soon as possible.