Maternal Autoimmune Thyroid Disease and Fetal Thyroxin

• Fetal free thyroxin [ Time Frame: 24th to 32nd week of gestation ] [ Designated as safety issue: Yes ]
  

• fetal ultrasound parameters [ Time Frame: 24th to 32nd week of gestation ] [ Designated as safety issue: Yes ]
  at the same time as fetal free thyroxin sampling
  
  
• maternal antithyroid antibodies [ Time Frame: 24th to 32nd week of gestation ] [ Designated as safety issue: Yes ]
  sampled at the same time as the fetal free thyroxin
  
  
• dose of maternal antithyroid medication (ATD) [ Time Frame: 24th to 32nd week of gestation ] [ Designated as safety issue: Yes ]
  recorded at the same time as the fetal sampling for free thyroxin
  
  

Maternal hyperthyroidism in pregnancy is complicated with hypertension, preeclampsia, heart failure, thyroid storm, preterm labor and stillbirth, while the fetus suffers from intrauterine growth retardation (IUGR), goiter; neonatal prematurity and low birth weight.

Maternal hypothyroidism is seen in 2 % of pregnancies. Risks are higher for preeclampsia, postpartum hemorrhage, miscarriage, stillbirth, preterm birth and lower IQ score.

Thyroid stimulating hormone (TSH) receptor antibodies, antithyroid drugs and iodine pass to the fetus. So the fetus may also become a patient. Monitoring fetal growth, fetal heart rate (tachycardia is a late sign of fetal hyperthyroidism), bone maturation and the size of the fetal thyroid by ultrasound are important parameters for the assessment of transfer of hyperthyroidism from mother to the fetus

Patients follow up:

After inclusion into the study, thyroid function tests (fT4, TSH), and auto-antibodies assessment (anti TPO, TRAK) were performed once every two months in mothers with AITD, and from the 24th week of gestation monthly. Treatment was adjusted accordingly. Ultrasound for fetal size, morphology and fetal heart rate (FHR) was performed once in two months, and from the 24th week of gestation, monthly. The fetal biophysical profile score was determined weekly from the 30th week of gestation. The single centre design was chosen: all fetal sonograms were performed by the same gynecologist. Cardiotocography was performed once weekly from the 30th week of gestation.

Study design:

Fetal and maternal free thyroxin (fT4) and TSH, thyroid antibodies in mothers and fetal ultrasound (fetal size, morphology and fetal heart rate) were determined at the same time, once, from 22nd to 33rd weeks of gestation.

Procedure: Cordocentesis (Cordocentesis is a highly specialized prenatal test in which a fetal blood sample is removed from the umbilical cord and tested for genetic problems, hormones or infections. Cordocentesis can be done at 18 weeks of pregnancy or later). Fetal fT4 and TSH were measured from cord blood samples. Healthy pregnant subjects were directed for cordocentesis for karyotype analysis due to age (missed previous procedures for karyotyping).

The diagnosis of fetal hypo or hyperthyroidism was established taking into account fT4 concentrations according to the nomograms Thorpee-Beeston et al., 1996, 1991.

When fetal hyperthyroidism is diagnosed, antithyroid drugs given to the mother are administered or adjusted. When fetal hypothyroidism is diagnosed, then the possibility of intraamniotic thyroxin application is discussed with the mother.