[Ultrasonic assessment of fetal thyroid function through ultrasound in pregnant women with hyperthyroidism]

To explore the value of prenatal ultrasound in assessing thyroid function in fetuses of hyperthyroidism pregnant women and establish the reference values of fetal thyroid transverse diameter and anteroposterior diameter for different gestational weeks.

For observation group, 30 cases of pregnant women diagnosed as hyperthyroidism were recruited from our hospital from November 2012 to November 2013. And another 100 cases of pregnant women during 20 to 40 weeks of gestational weeks were selected into control group. The measured ultrasonic parameters included fetal biparietal diameter, head circumference, abdominal circumference, femur length, amniotic fluid index, heart rate, fetal thyroid transverse diameter, anteroposterior diameter and fetal movement frequency. A fetus was considered as suspected positive when they were less than gestational age, thyroid measurement higher than 95% confidence interval, heart rate over 160 beats/min or less than 120 beats/min. In the observation group, the blood levels of thyroid stimulating hormone and thyroxine were measured after birth.

The regression equation of fetal thymus transverse diameter and GA was: Y = 0.053X - 0.096, R² = 0.758, P < 0.05; the regression equation of fetal thymus anteroposterior diameter and GA: Y = 0.034X - 0.397, R² = 0.596, P < 0.05. The measured value of 95% confidence interval for 2 cases in observation group exceeded that in control group. There were fetal tachycardia (n = 2), bradycardia (n = 1), low TSH after birth (n = 2), T4 elevation after birth (n = 1) and clinical T4 high value (n = 1).

Ultrasonic assessment of fetal thyroid function is timely and noninvasive. And it has an irreplaceable value in hyperthyroidism pregnant women. And normal reference values of fetal thyroid measurements are established for 20-40 gestation weeks.