Incident maternal infections during pregnancy/postpartum may
increase MTCT because of high levels of maternal viral load
during incident infection, low levels of passively transferred
maternal antibody, and absence of PMTCT ARVs because
maternal infection is initially undetected. While half of the studies
included in our MTCT rate analysis were conducted prior to implementation of PMTCT ARV prophylaxis, transmission rates
were similar among women receiving and not receiving ARVs. In
addition, although current World Health Organization guidelines
for PMTCT are shifting from short-course ARV regimens to
lifelong maternal ART, short-course regimens continue to be used
in many resource-limited settings [47]. Thus, our pooled MTCT
rates remain relevant to pregnant and postpartum women with
both undiagnosed and treated incident infections, and highlight
the need to improve detection of infections and early initiation of
PMTCT ARVs.