Knowledge of developmental biology is essential for clinicians who seek to develop a rational approach to the diagnostic evaluation of patients with birth defects. After an accurate diagnosis, a clinician can make predictions about prognosis, recommend management options, and provide an indication of recurrence risk for the parents and relatives. In this paper, we first review the basic mechanisms of embryological development and clinical dysmorphology. We then review cellular and molecular mechanisms in development and related congenital anomalies. Developmental anomalies have a major impact on public health. Genetic counseling and prenatal diagnosis, with the option to continue or to terminate a pregnancy, are important for helping families faced with the risk of a serious congenital anomaly in their offspring. Moreover, primary prevention of birth defects, for example, supplementation of prenatal folic acid and prevention of consumption of alcohol which has teratogenic effects, can be accomplished using developmental biology knowledge.