Maternal obesity is understood as a relevant factor in increasing the child's obesity risk, and Wiedmer and Herter-Aeberli show a narrative review of nutritional strategies to reduce obese pregnancy as a promising strategy to tackle this transgenerational diet-related disorder and comorbidities. The authors highlight the meaningful impact of short-chain fatty acids SCAFs, produced by gut microbes, on maternal and offspring health. Notably, in this last, the embryonic differentiation of enteroendocrine cells would be influenced by the action of SCFAs on the GPR43 receptor, making high-fiber dietary regimes a protector factor against predisposed adiposity. After a detailed assessment of the pre-clinical and clinical evidence published, the efficacy of probiotics in managing weight gain and metabolic function in mothers and offspring is blurred in both types of studies, probably due to the variability of trials and utilization of different probiotic formulations. However, prebiotic administration showed promising results, especially in the offspring's body weight control and metabolic function.

It's important to be aware of the cornerstone role of human milk as a nutrient source, immune defense, and as the seed of the infants' gut microbiota, thus influencing their health by extension. In this context, Gómez-Torres et al. have measured the impact of SARS-CoV-2 infection in the bacterial composition of human milk to unveil potential mid- and long-term alterations in offspring health as a consequence of the COVID-19 pandemic. This multicentre clinical study explored the human milk microbiota profiles of more than 140 mothers who decided to breastfeed their healthy babies regardless of whether they were positive or negative for SARS-CoV-2 infection at delivery. One week and 5 weeks postpartum milk samples were negative for detection of SARS-CoV-2, and they were assessed using standard 16S rRNA gene sequencing approaches. After recording critical perinatal variables for integration, the authors describe minimal impact of SARS-CoV-2 infection on human milk microbiota composition, getting similar patterns observed in other populations upon evaluating non-infected individuals.

This RT compiles another intriguing study trying to decipher the effects of pathogens transmitted from mothers to offspring via breastfeeding, thus with the potential to alter the health status and development of progeny. Morales-Ferré et al. present a comprehensive study on the immune profiling of rat pups upon oral administration of low-load and high-load Staphylococcus epidermis (a human mastitis pathogen) during lactation period. Despite the fact that the rat model of exposure to mastitis pathogen showed no changes in terms of offspring weight gain or intestinal physiology, but sustained oral administration of S. epidermis for 21 days (lactation period) does alter the circulating lymphocyte population as well as reduce the plasma Ig levels. Besides, exposure to S. epidermis during the lactation period also seems to drive an unbalance of Th1:Th2 signaling with potential short- and long-term effects on rat pups to clear infections and regulate immune response.

The infants' early life is critical to the development and health programming, resulting in long-lasting effects conditioning predisposition to a wide variety of infectious and non-communicable diseases as well as behavioral and mood dysfunctions. Consequently, Eow et al. propose an ambitious follow-up study (MYBIOTA) of mother-infant pairs during 12 months postpartum, in Malaysia, where they will collect and assess a wide array of clinical host-associated and molecular-derived data to understand the host-microbe interactions in the first year of life and disclose mother-derived and environmental determinants with high impact on the offspring health. Furthermore, with the longitudinal perspective, this study will also have the capacity to unveil the effects of such determinants on the development of fetuses, newborns and infants. All in all, this study will promise to fill the knowledge gap on the colonization and development of the gut microbiome during early life and to understand how it depends on mother interaction from the molecular and microbiological point of view.

The contributions gathered in this RT represent a clear advance in delineating how the maternal microbiome can modulate the offspring's health, paving the way for future studies and clinical application of the insights compiled here.

AB-P read all the contributions to the Research Topic and prepared this editorial.