This book investigates the evolutionary purpose of pregnancy sickness, proposing that it serves as a biological defense mechanism to protect the developing embryo from environmental toxins. Margie Profet, an evolutionary biologist, utilizes a Darwinian medical framework to argue that nausea and food aversions are not merely symptoms of hormonal shifts but are adaptive behaviors. By analyzing the timing of these symptoms, she posits that the female body actively shields the fetus during its most vulnerable period of organogenesis.

Experts in evolutionary medicine often cite this work as a provocative application of Darwinian principles to modern obstetrics. Readers frequently note that the prose is accessible to laypeople while maintaining a rigorous focus on biological adaptation.