Fertility is considered a ‘sixth vital sign’ because it can forewarn other health issues, including exposure to environmental toxicants. Coincident with an animal facility upgrade, our female mice exhibited profound loss of embryos during pre-implantation development. Extensive investigations uncovered that drinking water was the cause and water composition analysis was undertaken to identify the responsible toxicant(s). Trace elements were within recommended levels and phthalates undetectable; however, Per- and Poly-fluoroalkyl Substances (PFAS), a family of persistent organic pollutants and endocrine disrupting chemicals, were detected at 4.3ng/L. Compared to controls, mice exposed to the PFAS-contaminated water exhibited oocytes that were shrunken or had small polar bodies, and failed to form embryos. To investigate further, mice were given three local sources of drinking water contaminated with PFAS at 0.6ng/L, 2.8ng/L, or 4.4ng/L for 9 weeks (n=5-6/group). Mice consuming PFAS-contaminated water had decreased oocyte quality (p<0.04), 2-cell (p<0.02), and blastocyst development rates (p<0.004) compared to mice consuming PFAS-free (MilliQ) water. PFAS concentration was negatively correlated with oocyte viability (r=-0.89, p<0.0001). Alarmingly, these PFAS levels are representative of those in Australian drinking levels and well within current “safe level” guidelines. To directly test the effects of trace-level PFAS, a relevant mixture of PFOA, PFOS, and PFHxS at 5ng/L or 50ng/L was given to female mice for up to 6 months. Water for human consumption (drinking fountain) was included for comparison. Systemic effects were monitored and reproductive parameters analysed. PFAS exposure, even at these trace levels, was associated with extensive hair loss (n=29-47/group), altered ovarian folliculogenesis, decreased embryo mitochondrial function (n≥11, p<0.03), decreased blastocyst cell numbers (n=13-21, p=0.008), reduced fetal weight and size (n=12-27 fetuses from 2-3 pregnancies, p<0.01), and increased neonatal mortality. This data that water deemed suitable for human consumption has detrimental effects on mammalian embryo development has important implications for water quality policies.