Table 1.

Definitions of contributing factors

Contributing factor	Definition
Woman declined antenatal HIV testing	Clinicians reported that the woman was offered and declined HIV testing in pregnancy
Seroconversion	The woman acquired HIV infection during pregnancy or after delivery after initially testing negative
Problems with engagement or adherence	Clinicians looking after the woman in pregnancy reported that the woman had difficulties attending antenatal appointments (including appointments with their HIV clinicians), and/or adhering to antiretroviral therapy
Postnatal transmission probably attributable to breastfeeding	Clinicians reported evidence that the timing of the transmission was postnatal, in women diagnosed by delivery.
Woman presented late for antenatal care	The woman did not access antenatal care for the first time in the pregnancy until after 24 weeks of gestation
Woman transferred antenatal care provider	The woman was seen at more than one unit for antenatal care
Pre‐term delivery impact on duration of treatment	The infant was delivered pre‐term, and this impacted on the duration of antiretroviral therapy and therefore the woman's viral load at the time of delivery
Problem with antenatal HIV test	The woman was offered and accepted an HIV test in pregnancy, but the result was not available because of a processing or reporting error