Early and more recent data are conflicting in regard to whether ART during pregnancy is associated with adverse pregnancy outcomes, specifically with preterm delivery (before 37 weeks). Multiple observational studies have detected small but significant increases in preterm birth with PI-based and non PI-based ART. ^{[40, 41]} Conflicting findings may be influenced by a number of factors, e.g. data variability available for analysis, the time when ART was commenced, HIV disease severity (an independent factor), maternal age and intravenous drug use.

These findings should not prevent the current drugs from being used as the benefits of effective ART in pregnancy currently outweigh any concerns about an increased risk of preterm delivery.