Appetite sensations and nausea and vomiting in pregnancy: an overview of the explanations.

We review information about the potential mechanisms underlying nausea and vomiting in pregnancy (NVP), food cravings, and/or aversions in pregnancy. In addition to providing overviews about genetic predispositions and hormonal associations with appetite sensations and NVP, we review two functional explanations: the "maternal and embryo protection" and the "placental growth and development" hypotheses. We conclude with a discussion about the kinds of data that would enable us to better evaluate the relative advantages and disadvantages of NVP across disparate resource and ecological conditions.