Objective: To investigate the morphologic structures and developmental anomalies of the thyroid gland in human fetuses.

Methods: This study performed in the Department of Anatomy, Meram Faculty of Medicine between February and April in 2002. Fetuses were obtained from the Gynecology Department of the Meram Faculty of Medicine, Selcuk University, and Dr. Faruk Sukan Maternity Hospital (Konya, Turkey). Sixty spontaneously aborted fetuses (30 boys and 30 girls) between the ages of 13.5th and 32.5th weeks, which had no detectable anomalies, were evaluated. The gland was dissected under the microscope. The location of the gland was determined according to the tracheal ring levels and laryngeal cartilage levels. The length, width and thickness of both lobes and isthmus of the gland were measured and then, the developmental anomalies were noted. The obtained data were statistically analyzed by Least Squares in variant analysis.

Results: Although there was no significant difference regarding to the gender for all parameters except in width of the right lobe (p<0.05), difference in the length and width of lobes and the length of isthmus between trimesters was significant (p<0.05). All measured parameters were increasing with advancing gestational age. The pyramidal lobe was observed in 18.3% of the cases.

Conclusion: Normal dimensions and developmental anomalies of the fetal thyroid, which was shown in this study, may provide useful information for the prenatal diagnosis and in-utero treatment of thyroid dysfunctions.