Anatomical dimensions of larynx, epiglottis and cricoid cartilage in foetuses and their relationship with crown rump length.

BACKGROUND: Advances in perinatal care and increased use of diagnostic and interventional procedures on foetal airway demand a clear understanding of their normal anatomy and development. This study is aimed at determining the normal dimensions of larynx, cricoid cartilage and epiglottis and their correlation to age and crown rump length (CRL). METHOD: After approval from institutional ethics committee and written parental informed consent, laryngeal measurements were taken from 79 foetuses of varying CRL from 30 to 299 mm. The entire larynx from the tip of epiglottis to lowest extension of thyroid gland was isolated and preserved. In small foetuses (30-165 mm) the measurements were taken under a dissecting microscope. In foetuses above the CRL of 165 mm, the measurements were taken with help of Vernier Calliper. RESULTS: Foetuses were analysed for dimensions based on CRL. The length of the larynx significantly increased in comparison to CRL (P < 0.001). Similar measurements were observed for transverse diameter, anteroposterior diameter and inter-cartilaginous distance of larynx, the anterior height of arch and posterior height of lamina of cricoid cartilage and the length and breadth of epiglottis. The internal anteroposterior and transverse diameter of cricoid cartilage showed no correlation with CRL. CONCLUSION: All the measured parameters of larynx, epiglottis and cricoid cartilage showed positive correlation with the CRL except the internal diameters of cricoid.