Gustatory and olfactory shifts during pregnancy and the postpartum period: A systematic review and meta-analysis

Pregnancy is a transformative phase marked by significant behavioral and physiological changes. Substantial changes in pregnancy-related hormones are thought to induce changes in chemosensory perception, as often observed in non-human animals. However, empirical behavioral research on pregnancy-related olfactory or gustatory changes has not yet reached a consensus. This PROSPERO pre-registered systematic review and meta-analysis evaluated published data of olfactory and gustatory changes in pregnant individuals, across the three pregnancy trimesters and postpartum period. Our comprehensive search strategy identified 20 relevant studies, for inclusion in the meta-analysis. The metaanalysis revealed that pregnant individuals, regardless of trimester, performed significantly poorer in terms of odour identification, however, no difference was detected between non-pregnant controls and women postpartum. Additionally, pregnant women in the second and third trimester rated olfactory stimuli to be more intense. A slight decline in odour pleasantness ratings was observed amongst those in the second trimester. No major difference was observed between pregnant and non-pregnant subjects in terms of gustatory functions, except the first trimester appeared to be associated with increased pleasantness for the sweet taste. Post-hoc meta-regression analyses revealed that pregnancy stage was a significant predictor for observed effect size for odour intensity ratings, but not for odour identification scores. These findings provide valuable insights into the interplay between pregnancy and chemosensory perception, highlighting systematic physiological changes due to pregnancy. Healthcare providers can also utilize the knowledge of sensory shifts to better support pregnant women in making appropriate dietary choices, managing sense-related discomfort, and leading to potential sensory interventions. Overall, this research enhances our comprehension of sensory shifts during pregnancy, benefiting maternal health and pregnancy-related care.