Assessing Fetal Thyroid Function By Using Three-dimensional Ultrasonography And Detecting Amniotic Fluid Hormone Concentrations

Objective To evaluate the feasibility of fetal thyroid volume measurement by usingvirtual organ computer aided analysis(VOCAL) technique with three-dimensionalultrasonography(3D US) and normal values of thyroid were plotted as a function ofgestational age to establish a nomogram; and then normal reference range of hormoneconcentrations in amniotic fluid were also measured. We also evaluate the fetal thyroidfunction by three-dimensional ultrasound and amniocentesis.Methods Measurements of fetal thyroid were performed on16fetuses bytwo-dimensional ultrasonography(2D US), as well as3D US with VOCAL technique,and intra-and inter-observer reproducibility for measurement by2D US and3D USwere evaluated in our study, anatomical measurements in the end. A cross-sectionalstudy was performed on normal fetuses (n=330) and on fetuses with high-risk ofthyroids (n=387).The indicators of thyroid size of all normal fetal (including length,anteroposterior diameter, the maximum transverse diameter, perimeter, area andvolume) were measured by3D US and hormone concentration (including T3, T4, TSH,FT3and FT4) in amniotic fluid of172normal fetal were measured byelectrochemiluminescence immunoassay. And the thyroids and hormoneconcentrations in amniotic fluid of387high-risk fetuses were screened to assess thefetal thyroid function during the prenatal period.Results (1) A higher degree of reproducibility was observed in measurement of fetalthyroid volume by3D US than by2D US; the intraclass correlation coefficient (ICC)of intra-and inter-observer were0.993vs0.936and0.948vs0.924, respectively;ninety-five percent of uniform bounds were-0.060.06cm3vs-0.160.10cm3and-0.150.12cm3vs-0.220.17cm3, respectively.(2) Three hundred and eight out ofthree hundred thirty normal fetuses of gestational age between19and41weeks wererecruited. The regression equations between length(L), anteroposterior diameter(AD),the maximum transverse diameter(TD), perimeter(P), area(A) and volume(V)measured by3D US were expressed as follows: yL=0.06x+0.045(r=0.628, p0.05);yAD=0.025x+0.16(r=0.591, p<0.05); yTD=0.038x+0.224(r=0.600, p<0.05);yP=0.143x+0.016(r=0.604, p<0.05); yA=0.047x-0.373(r=0.529, p<0.05); yV=0.03x-0.315(r=0.566, p0.05).(3) There was a significant correlation betweenfetal FT3, T3values in amniotic fluid and gestational age; the regression formula wereyFT3=0.051x-0.551(r=0.668, p<0.05)； yT3=0.015x+0.799(r=0.712, p<0.05); nocorrelation was found between FT4, T4, TSH and gestational age(rFT4=0.423, p>0.05；rT4=0.321, p>0.05； rTSH=0.257, p>0.05).(4) Four fetuses with congenitalhypothyroidism were identified when using3D US-VOCAL technique combined withamniocentesis.Conclusions Fetal thyroid volume can be reproducibly measured by3D US-VOCALtechnique; a higher degree of reproducibility was observed in measurement of fetalthyroid volume by3D US-VOCAL technique than by2D US. Normal referenceintervals of fetal thyroid and normal reference range of hormone concentrations inamniotic fluid were established.3D US-VOCAL technique combined with thehormone concentrations in amniotic fluid can be a useful indicator of evaluation tofetal thyroid function status.