Objective: To track changes in olfactory performance during pregnancy and the postpartum.
Methods: In a prospective study the olfactory function of 38 pregnant women was assessed at about 12, 21, and 36 weeks of pregnancy and 7 weeks after delivery. A control group of 46 nonpregnant women were also asked to rate the intensity and hedonic tone of 10 "natural" odors.
Results: There was no difference in olfactory performance between the women in the first trimester of pregnancy and the controls, but at approximately 36 weeks of pregnancy the pregnant women experienced a decreased odor threshold compared with the nonpregnant controls, and this decrease was still present after delivery. There was no significant difference between the groups in capacity for odor discrimination or odor identification. "Objective" decreases were observed even though pregnant women rated their olfactory sensitivity significantly higher than the controls. Although the 2 groups did not differ with regard to intensity ratings of the 10 "natural" odors, there were differences with regard to the hedonic ratings.
Conclusion: Pregnancy is accompanied by changes in olfactory performance. Changes in hedonic odor ratings indicate a potential embryo-protective mechanism. The discrepancy between "objective" and "subjective" olfactory function may relate to changes in the cognitive processing of chemosensory information during pregnancy.