Effect of Pregnancy on Vocal Cord Histology: An Animal Experiment

Background: Voice may be affected during the period of pregnancy, especially in the third trimester. However, the exact mechanisms leading to the phonatory changes have not yet uncovered. Aims: The aim of this study is to investigate the possible histological changes in the vocal cords of the pregnant rats in three separate trimesters. Study Design: Animal experiment. Methods: Twenty-five Wistar-Albino female rats were divided into four groups: control group, pregnancy day 7 (Group 1), pregnancy day 14 (Group 2) and pregnancy day 20 (Group 3). The laryngeal specimens were obtained under general anesthesia. Histological assessment was performed using Hematoxylin-eosin and toluidine blue. A stereological analysis of vocal cord tissue was performed using a NIS-Elements D32 Imaging Software. Results: Lamina propria was observed to be edematous, and the lamina propria area was thickened starting from the second trimester. Glycosaminoglycans were observed to increase in the second trimester. Although none was encountered in the control, mast cells were observed in the lamina propria layer of the vocal cord starting in the muscular layer in the first trimester proceed to the subepithelial region as degranulated just before term. The covering epithelium remained unchanged throughout pregnancy. Conclusion: Lamina propria thickening may be attributed to both edema and increased glycosaminoglycans. The presence of mast cells in the cordal tissue may induce edema during pregnancy in rats.