Andrew Francis Dixon studied human anatomy and egg cells at the turn of the twentieth century in Ireland and Great Britain. Dixon studied the sensory and motor nervous system of the face, the cancellous bone tissue of the femur, supernumerary kidneys, and the urogenital system. In 1927 Dixon described a mature human ovarian follicle. This follicle, Dixon noted, contained an immature human egg cell (oocyte) with a visible first polar body and the beginnings of the second polar body. Dixon's work helped researchers describe many of the items found in follicles during the production of oocytes, and it helped them identify when, where, and how those items were produced. Based upon his descriptions, later researchers further described polar bodies and investigated their functions.

James Graves Wilson's six principles of teratology, published in 1959, guide research on teratogenic agents and their effects on developing organisms. Wilson's six principles were inspired by Gabriel Madeleine Camille Dareste's five principles of experimental teratology published in 1877. Teratology is the study of birth defects, and a teratogen is something that either induces or amplifies abnormal embryonic or fetal development and causes birth defects. Detailed in his 1973 monograph, Environment and Birth Defects, Wilson's principles helped scientists research teratogens experimentally.

Environment and Birth Defects by James Graves Wilson in the US was published in 1973. The book summarized information on the causes of malformations in newborns and aimed to acquaint policy makers with Wilson's suggestions for predicting the risks of environmental causes of birth defects, called teratogens. Wilson also provided six principles for researching teratogens, a framework revised from his 1959 article Experimental Studies on Congenital Malformations. The book has ten chapters. The body of the text is followed by three appendices that contain reference material and photographs of laboratory animals, and reproductive and embryological information.