The factors influencing mother-to-child cell trafficking and persistence over children’s lives have yet to be established. The quantification of maternal microchimerism was previously reported through HLA-based approaches, which introduced bias regarding the tolerogenic environment. We aimed to identify cells of maternal origin irrespective of the HLA repertoire and to ascertain the determinants of microchimeric cells. This case–control study enrolled 40 male infants attending pediatric surgery from January 2022 to October 2022. Female cells were quantified in infants’ tonsil tissue by using cytogenetic fluorescent in situ hybridization (FISH) coupled with optimized automated microscopy. Out of the 40 infants, half (47.4%) had been breastfed for more than one month, a quarter for less a month, and 10 children (26.3%) were never breastfed. XX cells were observed in male tonsils in two-thirds of participants at a median density of 5 cells per 100,000 cells. In univariate analyses, child age was negatively associated with a high female cell density. In exploratory multivariate analyses, previous breastfeeding is a likely determinant of the persistence of these cells in the host, as well as the rank among siblings. Part of the benefit of breastmilk for child health may therefore be driven by breastfeeding-related microchimerism.

Background and Aims: Since the discovery of human immunodeficiency virus (HIV) mother to child transmission (MTCT), its prevention has been a priority. Guideline adherence has drastically reduced MTCT, virtually inexistent today in high‐income countries. Methods: Our retrospective study included consecutive pregnant women with HIV who delivered in the Montpellier University Hospital between 2000 and 2020. We sought to examine our center's practices, outcomes, and illustrate the changes in management of pregnant women infected with HIV. Based on significant changes in French HIV guidelines and ART recommendations, we defined timelines for mode of conception, ART strategy, mode of delivery, and pediatric guidelines. These periods were compared to assess changes in our practice. χ ² test, Fisher's exact test, Kruskal–Wallis H test, and Cochran–Armitage test were used when appropriate. Results: We included 144 women and report a total of 194 pregnancies—of which 39 repeat pregnancies and 9 twin pregnancies—resulting in 201 live births. Between 2000 and 2020, 27 (13.9%) women discovered their HIV‐positive status during pregnancy. Over these 20 years, maternal antiretroviral therapy (ART) was started progressively earlier during pregnancy ( p < 0.01), planned ART interruptions became less frequent ( p < 0.01), and monotherapy was increasingly replaced by boosted triple therapy ( p < 0.01). Frequency of vaginal deliveries increased ( p < 0.01), and intrapartum intravenous Zidovudine was seldom used after 2013 ( p < 0.01). Approximately 98% of newborns received antiretroviral prophylaxis at discharge, and 91.3% of infants had at least 6 months of follow‐up. We observed only one case of MTCT in 2000. Conclusion: Our study illustrates the major changes for the prevention of HIV MTCT. Our findings highlight how early and effective triple ART led to better obstetrical outcomes requiring fewer medical interventions. Thorough treatment, aligned with national guidelines, can virtually eliminate MTCT, serving as a model for global practice.