To investigate the association between INSTI vs non-INSTI containing regimens on weight gain during pregnancy. This is a retrospective cohort study of women with HIV on ART, delivered at Grady Memorial Hospital, 2011 - 2019. The primary outcome was incidence of excessive gestational weight gain in pregnant women receiving ART containing INSTI, TAF, tenofovir disoproxil fumarate (TDF), or neither. Excess gestational weight gain (adjusted for gestational age at delivery) was defined based on pre-pregnancy body mass index (BMI) using IOM definitions, and was adjusted by weight gain rates if prenatal care was initiated after the first trimester. Treatment effects were estimated by ART regimen type using log-linear models for relative risk, adjusting for pre-pregnancy BMI, gestational age of first weight measurement and presence of detectable viral load at baseline. Chi-square and Fisher’s exact test were used to compare categorical variables. A p value less than 0.05 was considered statistically significant. A total of 305 pregnant women with HIV were included in the following ART groups: (1) INSTI with TAF: 38 (12.5%); (2) INSTI with TDF: 39 (12.8%); (3) INSTI without TAF or TDF: 12 (3.9%); (4) non-INSTI with TAF: 2 (0.7%); (5) non-INSTI with TDF: 110 (36.1%); and (6) non-INSTI without TAF or TDF: 104 (34.1%). Baseline variables including pre-pregnancy BMI, viral load at prenatal care entry, use of ART before pregnancy, and gestational age at delivery were similar across ART groups (p = NS). Compared with women who received non-INSTI ART without TAF or TDF, receipt of INSTI+TAF had a 1.74-fold increased risk of excess weight gain, (95%CI 1.15 – 2.65, p< 0.01), while INSTI without TAF or TDF was not significantly associated with excess weight gain, nor was the interaction between INSTI and TDF, in this population. The effect of TAF without INSTI could not be inferred from our data. There was no difference in neonatal, obstetric, or maternal outcomes between the groups. Pregnant women receiving ART with INSTI and TAF have increased risk of excess gestational weight gain.View Large Image Figure ViewerDownload Hi-res image Download (PPT)