If an infant is born to an HIV positive mother, will the infant always have the HIV antibody at birth? If the mother was recently infected would the HIV antibody still be present in the newborn?

Fetuses and young infants generally do not make antibodies very well and most antibodies (including HIV antibodies) present at birth are passed to the baby from the mother during the last trimester of pregnancy (after 24 weeks gestation). If a mother has established HIV infection and made an antibody response, these antibodies would be passed to her full-term baby; however, premature babies might not receive the full complement of antibodies. If a mother acquires HIV infection during the last trimester of pregnancy and delivers before making a full antibody response, the baby could lack HIV antibodies.