Re-examining the adaptive function of nausea and vomiting in pregnancy.

Nausea and vomiting in pregnancy (NVP) have been proposed to have a prophylactic function. In this review, I re-examine NVP from an evolutionary perspective in light of new research on NVP. First, current evidence suggests that the observed characteristics of NVP does not align well with a prophylactic function. Further, NVP is typically associated with high costs for pregnant women, while moderate-to-severe NVP is associated with increased risks of poorer foetal/birth outcomes. In contrast, mild NVP limited to early pregnancy may associate with improved foetal outcomes-indicating a potential evolutionary benefit. Second, researchers have recently identified growth differentiation factor 15 (GDF15) to cause NVP, with implications that low-levels of pre-conception GDF15 (associated with lower cellular stress/inflammation) may increase risks/symptoms of NVP. If so, NVP in contemporary post-industrialized populations may be more severe due to environmental mismatch, and the current symptomology of NVP in such populations should not be viewed as a typical experience of pregnancy.