Early life represents a critical window for metabolic, cognitive and immune system development, which is influenced by the maternal microbiome as well as the infant gut microbiome. Antibiotic exposure, mode of delivery and breastfeeding practices modulate the gut microbiome and the reservoir of antibiotic resistance genes (ARGs). Vertical and horizontal microbial gene transfer during early life and the mechanisms behind these transfers are being uncovered. In this review, we aim to provide an overview of the current knowledge on the transfer of antibiotic resistance in the mother-infant dyad through vertical and horizontal transmission and to highlight the main gaps and challenges in this area., This work has been supported by PROMETEO GVA (NEOHEALTH ref. 2020/012). The authors acknowledge the comments and suggestions of Dr. Raul Cabrera-Rubio. who thanks the Generalitat-Valenciana for the grant of the Plan GenT project (CDEIGENT 2020). M.B. thanks to the post-PhD grant 'Juan de la Cierva' (ref. JDC2022-050269-I) supported by the Spanish Ministry of Science, Innovation and Universities/State Investigation Agency (MCIU/AEI) and the European Union 'NextGenerationEU'/PRTR. E.C-Y received a FPI predoctoral fellowship from the Spanish Ministry of Science and Innovation with identifier PRE2020-092531. E.F.V thanks to a Predoctoral grant awarded by the Spanish Ministry of Science and Innovation and the European Social Fund Plus (ESF+) for the training of doctors within the framework of the State Plan for Scientific, Technical and Innovation Research 2021–2023 (ref. CEX2021-001189-S-20-1). A.S. acknowledges Generalitat-Valenciana-European Social Fund (ACIF/2021) for the predoctoral fellowship grant. M.C.C. acknowledges the support by the European Research Council Starting grant (MAMI grant ref. 639226), Horizon Europe Program (INITIALISE ref. 101094099), Spanish Ministry of Science and Innovation (MAMI-Plus ref. PID2022-139475OB-I00), by the Joint Action 'European Joint Programming Initiative “A Healthy Diet for a Healthy Life” (JPI-HDHL)' — FOOD-HYPERSENS call (ECOBIOTIC) and the national funding from Programación Conjunta Internacional (PCI) (ref. PCI2021-122059-2A), Spanish Government (Ministry of Science, Innovation and Universities) and also by Biostime Institute Nutrition & Care (BINC) grant. IATA-CSIC authors also acknowledge the Spanish government Ministry of Science and Innovation/State Investigation Agency (MCIN/AEI) to the Center of Excellence Accreditation Severo Ochoa (CEX2021-001189-S/MCIN/AEI/10.13039/501100011033). A.M. acknowledges the support by grants PID2019-108541GB-I00 and PID2022-137201NB-I00 from Spanish Government (Ministry of Science and Innovation). M.C.C. and A.M. are part of the CSIC's Global Health Platform (PTI Salud Global)., Peer reviewed