Marked changes in olfactory perception during early pregnancy: a prospective case-control study

Pregnancy seems to be related with a significant change in olfaction. Here, we investigate this theory by testing the odor identification abilities of uncomplicated pregnant women and compare the results with non-pregnant controls. The study included 31 healthy pregnant women in the first trimester (Group 1), 30 in the second trimester (Group 2), 31 in the third trimester, and 30 non-pregnant healthy controls (Group 4). In order to measure odor identification abilities, each subject completed the 12-item Brief Smell Identification Test (BSIT). Next, the demographic characteristics and BSIT scores of the groups were compared. The total BSIT scores of the subjects in Group 1 were found to be significantly lower than those of the other groups (p < 0.001). This reduction in odor identification abilities was particularly noticeable for leather, pine, and soot. Pregnant women in the second and third trimesters had similar odor identification abilities to the healthy controls (p > 0.05). Early pregnancy might be related to significant changes in olfactory performance. The distortion of odor identification in the first trimester might be a causative factor for the development of pregnancy-specific conditions, such as morning sickness and hyperemesis gravidarum, which are both common complaints during the early phase of parturition.