Nomograms of fetal thyroid measurements estimated by 2-dimensional sonography.
OBJECTIVE
To build nomograms of fetal thyroid circumference (FTC), fetal thyroid area (FTA), and fetal thyroid transverse diameter (FTTD) throughout gestational age (GA).


METHODS
Between January 2006 and July 2006, FTC, FTA, and FTTD were measured once in 196 normal fetuses examined at a GA of 22-35 weeks. Inclusion criteria were a healthy mother with normal maternal thyrotropin level during pregnancy, a singleton pregnancy with normal fetal morphology on sonography, and GA confirmed via first-trimester sonographic examination.


RESULTS
Mean FTC, FTA, and FTTD ranged from 3.21 cm, 0.58 cm(2), and 1.19 cm at 22 weeks to 5.11 cm, 1.69 cm(2), and 1.89 cm at 35 weeks, respectively. Linear regression analysis yielded the following formulas for FTC, FTA, and FTTD according to GA: FTC (cm) = 0.146 x GA (weeks); FTA (cm(2)) = -1.289 + 0.085 x GA (weeks); FTTD (cm) = 0.054 x GA (weeks). The following logarithmic formulas were obtained for the expected fetal thyroid measurements according to estimated fetal weight (FW): FTC (cm) = -4.791 + 1.265 x logN FW; FTA (cm(2)) = -1.676 + 0.455 x logN FW; and FTTD (cm) = 0.399 + 0.001 x logN FW.


CONCLUSIONS
We describe new nomograms of fetal thyroid measurements throughout gestation that may be useful in case of thyroid dysfunction.
Bernardes
Lisandra Stein
LS
Obstetrics Department, Faculdade de Medicina da Universidade de São Paulo, Av. Dr. Eneias de Carvalho Aguiar, 255, São Paulo 05403-000, Brazil.
Ruano
Rodrigo
R
Sapienza
Andreia David
AD
Maganha
Carlos Alberto
CA
Zugaib
Marcelo
M
D005260:Female; D005865:Gestational Age; D006801:Humans; D016014:Linear Models; D049451:Nomograms; D011247:Pregnancy; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000196:embryology*; D016216:Ultrasonography, Prenatal