Fetal thymus reference range in healthy singleton pregnancies

Objective: To present the reference range of fetal thymus gland according to gestational age groups. Methods: In this prospective study, size was assessed in singleton, uncomplicated pregnancies between 19 and 38 weeks gestation our outpatient clinic 2019 2020. Based on their monthly pregnancy follow-ups, measurement divided into 5 groups (Group 1: 19–22 weeks, Group 2: 23–26 3: 27–30 4: 31–34 5: 35–38 weeks). Results: Fetal measurements 210 patients were performed over one year, as a result, 184 pregnant included for assessment. could be visualized at rate 93.5%. The 5th percentile transverse diameter, antero-posterior perimeter, anterior-posterior diameter thoracic perimeter circumference 11.03 mm, 5.60 32.52 0.33, 0.32 1; 13.53 7.66 43.67 0.34, 2; 20.43 11.22 47.72 3; 27 12.98 55.88 0.32, 0.30 4; 28 13.59 63.4 5; respectively. Spearman’s rho correlation coefficients thymic 0.879, 0.869, 0.846, 0.236, 0.267 respectively, all p-values less than 0.001. As result linear regression analysis BPD; equations optimal models are follows: diameter= -3.49+0.4xBPD (mm) (r=0.826, R2=0.682, p<0.001), -2.48+0.22xBPD (r=0.808, R2=0.653, perimeter= -14.37+1.21xBPD (r=0.814, R2=0.663, /thoracic 0.38+7.76E-4xBPD (r=0.213, R2=0.045, p=0.004) perimeter/thoracic circumference= 0.35+1.02E-3xBPD (r=0.263, R2=0.069, p<0.001). Thymus increased linearly with increasing biparietal (BPD). Conclusion: We established ranges size. have strong relationship easy reproducible. Therefore, knowledge will enable evaluation aplasia/hypoplasia.