Since 2017, dolutegravir (DTG), a second-generation integrase inhibitor (INI) with a high genetic barrier, has been part of first-line HIV treatment together with tenofovir and lamivudine. Resistance mutations (RMs) to this regimen are rare. In a recent systematic review, RM rates among treatment-naïve patients with virologic failure (VF) ranged from 0.3% to 1.9%. In contrast, Diaz et al. analyzed 113 treatment-naïve PLHIV who experienced VF on first-line therapy between July 2017 and December 2018 and reported major DTG mutations in 6.19% and accessory mutations in 14.2%. An Argentinian study of 52 pregnant women found no major mutations using next-generation sequencing. INI use in pregnant women in Brazil became more frequent from 2018 onward. This study aimed to describe INI resistance mutations and HIV-1 subtypes among pregnant women living with HIV genotyped in Rio de Janeiro from 2018 to 2024.

We used the SISGENO database to identify pregnant women in Rio de Janeiro who had integrase genotyping between 2018 and 2024. Subtypes were obtained from genotyping results at laudo.aids.gov.br. Resistance mutations were classified according to the 2025 IAS-USA mutation list.

Of 266 pregnant women genotyped during the period, 73 (27.4%) had the integrase region amplified; of these, 28 (38.3%) were INI-naïve. Two accessory mutations (T97A, G163K) and one major mutation (E138K) were identified. Reversion of T97A was observed on subsequent genotypes. The most prevalent subtype was B: 58 (79.5%), followed by F1: 7 (9.6%), C: 3 (4.1%), and five recombinants across PR/RT and INI regions (F/B, F/C, B/F).

A low frequency of resistance mutations to integrase inhibitors was observed among pregnant women living with HIV in Rio de Janeiro between 2018 and 2024. The presence of only one major mutation (E138K) and two accessory mutations (T97A, G163K), along with spontaneous reversion of T97A on follow-up genotyping, reinforces the high genetic barrier of second-generation INIs. To our knowledge, this is the first study to describe INI resistance mutations in pregnant women living with HIV in Rio de Janeiro and the largest case series to date. These findings contribute to local knowledge on primary resistance and underscore the need for ongoing molecular surveillance.