There has been a growing interest in assessing placental biometric parameters and their relationship with obstetric outcomes, highlighting their utility in reflecting changes in fetal development and long-term health. However, research focus on fetal development over the placental has caused many gaps in our knowledge about the biological role of placental abnormalities. This study aims to establish reference percentile curves for placental and fetal biometric parameters using data from Portuguese parturients. Nonlinear regression models, including Generalized Additive Models for Location, Scale, and Shape (GAMLSS) and Lambda-Mu-Sigma (LMS) methods, were chosen due to their flexibility in handling diverse statistical distributions. The application of the GAMLSS method with Box-Cox t (BCT) distribution and P-splines to Diameter 1, Diameter 2, Placental Volume, and FW/PW Ratio parameters, and LMS Box-Cox t (LMST) method to Placental Thickness, Placental Weight, and Fetal Weight parameters, results in representative percentile growth curves. This study successfully developed placental growth curves using nonlinear regression models, providing valuable information on placental development and its clinical implications in obstetrics. The reference growth curves enhance the monitoring of maternal-fetal health and can guide clinical decisions, especially in addressing contemporary challenges, such as low birth rates and increasing maternal age.