Anatomical, physiological, and metabolic changes during pregnancy can affect the absorption, distribution, metabolism, and excretion of several drugs. Risperidone is commonly prescribed for managing schizophrenia, but its prescriptions for pregnant women are restricted to circumstances in which the benefits outweigh the risks to the fetus. Therefore, current knowledge on optimal dosing regimens and safety characteristics during pregnancy, fetal, and neonatal periods is limited. We determined serum concentrations of risperidone and its active metabolite paliperidone in a pregnant woman and her newborn. Physiologically-based pharmacokinetic (PBPK) models for risperidone and paliperidone were developed in adult, pediatric, and pregnant populations and verified using the Simcyp simulator. These models were then applied to our two subjects, using “virtual twin” approach. Effects of pregnancy and ontogeny on pharmacokinetics of both drugs were examined using developed PBPK models with fixed parameters. PBPK model-informed approach could help with the precision dosing in special populations, such as pregnant women and neonates.