The IPOP trial demonstrated a reduced risk of severe small for gestational age among infants born to women with HIV who received weekly intramuscular 17 alpha-hydroxyprogesterone caproate. This secondary analysis examined the 17P treatment effect in subgroups of maternal body mass index, parity, timing of ART initiation, and ART regimen. We found 17P was more effective among nulliparous women, women who started ART before pregnancy, and those taking protease inhibitors
