Design of the present analysis

This study is a secondary analysis designed to investigate demographic, baseline clinical, and post-entry obstetrical risk factors associated with preterm delivery and low birth weight, along with the composite outcomes defined above. Note that the analyses for PTD, VPTD, LBW and VLBW were limited to pregnancies with at least one live birth (N=3333), while the analyses with the composite outcomes also included 90 singleton pregnancies whose only outcomes consisted of stillbirths or spontaneous abortions, yielding a total sample of N=3423. These analyses assessed the independent effects of known and suspected risk factors on adverse pregnancy outcomes, and evaluated the extent to which they might have mediated the ART treatment effect on adverse birth outcomes.

Predictor variables included in this secondary analysis were as follows:

baseline maternal clinical and demographic factors: maternal age, maternal body mass index (BMI), gestational age, country, treatment group, CD4 count, HIV viral load, multiple gestation, history of prior preterm birth, history of cigarette smoking, history of alcohol use, and HBsAg status. All were assessed at entry except for maternal age, which was assessed at delivery.

maternal obstetrical risk factors identified post randomization and throughout the pregnancy: abruptio placentae, placenta previa, chronic hypertension, pregnancy induced hypertension, polyhydramnios, oligohydramnios, intrauterine growth restriction, preterm labor, premature rupture of membranes, vaginal bleeding, lower genital tract infection, and urinary tract infection (UTI).