Pregnancy sickness: a biopsychological perspective.

Pregnancy sickness is a universal phenomenon, affecting 70% to 85% of all pregnant women. The primary symptoms of pregnancy sickness are nausea, vomiting, and food aversions. In the past, pregnancy sickness was attributed to psychological disturbances of the pregnant woman. However, recent evolutionary psychological and biopsychological studies have reconsidered pregnancy sickness as an embryo-protective mechanism, an evolutionary adaptation to protect the embryo from phytotoxins and other environmental hazards. The biopsychological perspective of pregnancy sickness as an embryo-protective mechanism is presented.