Fetal thyroid in two-dimensional ultrasonography: nomograms according to gestational age and biparietal diameter

European Journal of Obstetrics & Gynecology and Reproductive Biology, 06/01/2012

Authors have established age–dependent and age–independent nomograms of fetal thyroid. These nomograms will enable prenatal diagnosis in fetuses at risk of thyroid disorders.

Methods

  • A cross–sectional study of 241 healthy pregnant women at 14–38 week of gestation was undertaken.
  • Exclusion criteria were: known maternal thyroid or systemic disease, unknown date of last menstrual period, multiple pregnancy and fetal malformations.
  • Fetal thyroid diameter (FTD), circumference (FTC) and area (FTA) were measured by two–dimensional ultrasonography and plotted against gestational age (GA) and biparietal diameter (BPD).

Results

  • FTD, FTC and FTA increased logarithmically to GA and BPD.
  • Fetal thyroid measurements as a function of GA were expressed by logarithmic formulas: ln(FTD)=3.6025–23.0315/GA, ln(FTC)=4.6227–22.8003/GA, ln(FTA)=6.6303–45.0831/GA.
  • The following logarithmic formulas were obtained for fetal thyroid measurements according to BPD: ln(FTD)=3.4068–45.4271/BPD, ln(FTC)=4.4271–44.8359/BPD, ln(FTA)=6.2390–88.4408/BPD.
  • There were highly significant correlations between thyroid measurements and GA or BPD: r=0.87–0.90, p<0.00001.

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