Abstract
To compare the olfactory functions of pregnant and non pregnant females draining the tribal tertiary care centre. Odor identification (OI), odor discrimination (OD) and odor threshold (OT) in subjects and control group with no previous Sino-nasal symptoms or pathology were included in the study. Mean scores of all the parameters were calculated in both the groups. Group A being of 60 pregnant females in 1st trimester and Group B constituted 60 non pregnant females as control group. Both the groups were matched for Age and Normal Mucociliary clearance range. Modified Indian Smell Identification Kit was used to assess all parameters. Before doing objective olfactory assessment all the study participants were given questionnaire for subjective assessment of olfaction in which we found significant impairment in drinking beverage and fragrance perception of flowers in pregnant females compared to non pregnant females. We also found there was no significant difference in mean scores of various olfactory parameters in multigravida and non pregnant females. The mean OI score in both groups was 9.54 ± 1.87 and 8.70 ± 1.62 respectively. Mean OD score of the two groups was 8.80 ± 2.61 and 9.80 ± 2.61 respectively and the mean OT score of both the groups was 6.99 ± 4.63 and 4.13 ± 2.48 respectively.
Keywords: Olfaction, Pregnancy, Smell identification test
Introduction
Olfaction is considered to be the ability to perceive, conduct and recognize scents and odors [1]. Estrogen and Progesterone balance is known to have protective effect on olfaction. So their imbalance or dysbalance may affect the olfactory function in pregnant females and may be related to smell changes in pregnancy.
The most consistent source of evidence of smell changes in pregnancy comes from anecdotal reports and questionnaire studies [2]. The change in the level of reproductive hormone at the different trimesters of pregnancy has been documented to produce a significant change in olfactory function of pregnant mothers. Cognitive processing of odors appears to change in early pregnancy [3–6].
In our study we tried to explore the untouched area of otolaryngology so as to help in adding up for hypothesis of smell disorders in pregnancy and put forth a base for further studies for betterment of sense of smell and in turn taste and better nutritional need fulfillment of mother and baby during pregnancy and thus improving quality of life during pregnancy.
Material and Methods
Study was conducted in a Tribal Tertiary care centre of Northern Maharashtra after obtaining Scientific Committee and Ethical Committee clearance. Indian smell identification test was modified suiting to local availability and familiarity to the study subjects of our study. The test was used to detect odour identification ability, hedonicity and intensity of odorants presented to 60 pregnant females in 1st trimester and 60 non pregnant females. Both groups were matched for age and mucociliary clearance time and without any history of previous sinonasal disease per se. SPSS software version 26 was used to calculate mean scores and significance values, Pearson chi square test and two tailed t test was specifically used.
Odor Identification
Essence of 10 commonly used items—cardamom, clove, lemon, mango, orange, pineapple, rose, peppermint, eucalyptus and thinner were used for odour identification. Cotton buds dipped in the essence were used as test material which were placed 1 cm in front of one nostril and the other being closed and vice-versa for other nostril and repeated for all 20-ml air tight bottles of different odorants and mean score was calculated based on number of correct responses. For correct identification, score given was 1 for each nostril separately and wrong response was labeled as 0.
Odor Threshold
1-Butanol is the standard odorant used for OT testing. 1-butanol was used in serial dilutions in 10 bottles from minimum of 0.016% to maximum of 8% prepared in our biochemistry laboratory. Scores of 1 to 10 were given depending on the lowest concentration of solution successfully identified. For correct identification, score 1 was given and for non identification, score 0 and mean was calculated.
Odor Discrimination
Odor discrimination was tested by making 5 sets of 3 odourants, 1-butanol being common in all the sets. For each set four forced choices were given and mean discrimination score for each female in both case and control groups were calculated.
All the three parameters were statistically analyzed and significance value was obtained by chi-square test in between the two groups (Table 1). Subjective assessment was done by statistical analysis of self validated questionnaire of 11 questions (Fig. 1).
Table 1.
Table of Mean Scores of all olfactory parameters
| Olfaction parameters | Pregnant | Non pregnant | P value |
|---|---|---|---|
| OT (Threshold) | 9.54 ± 1.87 | 8.70 ± 1.62 | 0.0001 (HS) |
| OI (Identification) | 8.80 ± 2.61 | 9.80 ± 2.69 | 0.0097 (HS) |
| OD (discrimination) | 6.99 ± 4.63 | 4.13 ± 2.48 | 0.0410 (S) |
Fig. 1.
Smell Questionnaire of pregnant females in 1st trimester
Results
A self validated questionnaire responses on likert scale were statistically analyzed for pregnant primi and multigravida females and also for non pregnant females. It showed perception of one’s own body odour (p = 0.006) was significantly higher in primi compared to multi and non pregnant females. There was significant impairment in taking various drinking beverages (p = 0.029) because of hedonicity and also similar impairment was noticed for perceiving scent of flowers (p = 0.05). Two tailed t test was applied to compare mean scores of pregnant and non pregnant females and all the three olfactory parameters in our study showed significant difference (Table 1).
Discussion
A proper functioning sense of smell allows a person to discriminate between thousands of largely organic, low molecular mass, volatile compounds and provides information regarding:
Safety of a substance or environment
The aesthetic properties of everyday objects and elements of basic communication (e.g. mother/infant interactions)
When combined with gustatory and somatosensory stimuli the sense of smell determines the flavors of food and normal gastrointestinal secretions [7]. Demarquay et al. [8] used the term hedonicity for the pleasantness of smells and reported that patients with olfactory hypersensitivity judged odour less pleasant [8]. In our study also pregnant females had lower threshold of odour perception which is indicator of olfactory hypersensitivity and so were intolerant to perfumes and drinking flavored beverages and even perceived self body odour.
Kölbe et al. [9] found no significant difference in olfactory threshold between non pregnant and pregnant females [10]. This is in contrast with our study as mean scores of two groups are 6.99 ± 4.63 and 4.13 ± 2.48 respectively, lower in pregnant females and was statistically highly significant (p = 0.0001).
Gilbert and Wysocki [10] compared odour identification in pregnant and non pregnant women using 6 odour groups and found pregnant females were able to identify clove significantly more readily [9]. In our study we used 10 odorants in different combinations and found eucalyptus was more readily identified by pregnant females.
Cameron [2] measured odour identification in pregnant and non pregnant women and it was not statistically different. In our study overall difference in mean odour identification score of 2 groups is statistically significant (P = 0.0097).
In our study odour discrimination score was poor in pregnant females compared to non pregnant females (Mean score = 4.13 ± 2.48/6.99 ± 4.63). This is in contrast with the study conducted by Hummel et al. [4].
Conclusion
Pregnancy and olfaction is still the topic of future research as large scale studies are needed to prove whether the olfactory system per se is affected or it is odor dependent. We need to test odour identification threshold and discrimination over wide range of odorants and a group of common odorants which are less perceived or more hedonic are to be identified. Our study provides supportive evidence to the innumerous anecdotal data about smell changes in pregnancy especially first trimester. So, alteration in olfaction during pregnancy cannot be just a MYTH; it needs to be studied vastly and in depth.
Funding
This study was not funded by anyone.
Compliance with Ethical Standards
Conflict of interest
Leena Jain, N.K. Vashisht, Shalini Jadia, Pooja Nayak, Manish Jain declare that they have no conflict of interest.
Ethical Approval
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed Consent
Informed consent was obtained from all individual participants included in the study.
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