This document summarizes the development of the reproductive system from the indifferent stage through the formation of male and female external genitalia. It describes how the gonads initially develop from the urogenital ridge as indifferent structures before sex determination occurs. In males, the SRY gene causes testes to form which secrete testosterone and AMH to develop the male duct system and external genitalia. In females, the absence of SRY and testicular hormones allows the Müllerian ducts to form the female reproductive tract while the gonads become ovaries. Common birth defects affecting the reproductive system are also listed.