Jakob Rueff (1500-1558) a 16th century physician in Zurich practiced mainly as a surgeon but also possessed responsibility for training midwives. Rueff wrote De conceptu et generatione hominis, first published four years before his death, as basically a manual for midwives. Printed in both Latin and German, De conceptu was later translated into English as The expert midwife. What makes De conceptu such an important work is its emphasis on the study and detailed illustrations of anatomy in relation to obstetrics. Thus De conceptu, while primarily a text for midwives, was also used by surgeons and remained functional for over a century.

Divided into six sections or "books" the volume covers the entire pregnancy cycle along with discourses on related medical diseases and situations.

• Book one opens with information on conception and nutrition of the fetus.
• The second section contains descriptions of the uterus and guidelines for the pregnant women.
• Book three deals with the birthing process, subsequent care of mother and infant, as well as a portion devoted to the use of obstetric instruments.
• Section four pertains to the management of "unnatural" births such as multiples and awkward presentations.
• Book five discusses related conditions such as false pregnancy, uterine tumors, abortions, and deformed infants (or "monsters").
• Section six discusses causes for sterility with suggested remedies.

Woodcuts within the book include images of the birthing chair, anatomical drawings (based on Vesalius), the birth scene, obstetrical instruments, the developing ovum and illustrations of various positions of the fetus within the uterus, as well as images of deformed infants.

Critics of Rueff’s work consider it primarily a reworking of Eucharius Rosslin’s earlier work, Der swangern frauwen und hebammen Roszgarten, published in 1513. While Rueff’s book does follow the lead of Roszgarten, De conceptus provides a greater emphasis on anatomy and contains information from Rueff’s own obstetrical experiences. The introduction of new obstetrical instruments such as the toothed duck beak forceps and the use of internal and external manipulation for footling presentations verify Rueff’s practical experiences. With the suggested use of manipulation in the birth process, Rueff antedated both Marmaduke Wright of Cincinnati (1854) and Branxton Hicks of England (1860). The influence of De conceptus through the years is revealed by the title page of the 1637 English translation that stated the book was "translated into English for the generall [sic] good and benefit of this Nation."