Relations between the fetal circulation and pituitary-thyroid function.
OBJECTIVE
To study the relation between changes in the fetal thyroid hormone and thyroid stimulating hormone (TSH) concentrations and alterations in the fetal circulation as assessed by Doppler ultrasound.


METHODS
A cross-sectional study of small for gestational age (SGA) and red-cell isoimmunized fetuses undergoing cordocentesis and Doppler studies for the assessment and determination of fetal karyotype, acid-base balance and haemoglobin concentration.


METHODS
Harris Birthright Research Centre for Fetal Medicine, King's College, London.


METHODS
38 growth retarded and 38 red-cell isoimmunised fetuses.


METHODS
Cordocentesis.


METHODS
Serum TSH total and free thyroxine (T4, FT4) and total and free triiodothyronine (T3, FT3) concentrations; middle cerebral artery (MCAVm) and descending thoracic aorta (AoVm) mean blood velocities; fetal Po2 and haemoglobin concentration (Hb).


RESULTS
Delta values (delta) calculated as the number of SDs from the respective normal mean for gestation were used to compare the results with those from a previous study of normal fetuses. Mean AoVm was increased in the isoimmunized fetuses (P less than 0.001) but decreased in the SGA fetuses (P less than 0.001). Mean MCAVm was increased in both groups (P less than 0.01; P less than 0.001). There were significant associations between the gestational age adjusted values for TSH and MCAVm (r = 0.23, P less than 0.05) and between T4, FT4 or FT3 and AoVm (r = 0.41, P less than 0.01; r = 0.50, P less than 0.01; r = 0.36, P less than 0.01 respectively). In addition, T4 and FT4 were associated with delta Po2 and delta Hb.


CONCLUSIONS
In the hypoxaemic hypoxia of growth retardation and the anaemic hypoxia of rhesus disease there are significant associations between changes in fetal thyroid hormone concentrations and changes in fetal blood flow as assessed by Doppler. Irrespective of whether altered blood flow is the cause or effect of changes in thyroid hormone concentrations, the observed changes could have beneficial effects for fetal survival, in the presence of a hostile intrauterine environment.
Thorpe-Beeston
J G
JG
Department of Obstetrics and Gynaecology, King's College School of Medicine and Dentistry, Denmark Hill, London, UK.
Nicolaides
K H
KH
Snijders
R J
RJ
Felton
C V
CV
Vyas
S
S
Campbell
S
S
D001775:Blood Circulation; D003430:Cross-Sectional Studies; D005260:Female; D005312:Fetal Blood; D005317:Fetal Growth Retardation / Q000503:physiopathology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D010902:Pituitary Gland / Q000503:physiopathology*; D011247:Pregnancy; D012203:Rh Isoimmunization / Q000503:physiopathology*; D013961:Thyroid Gland / Q000503:physiopathology*; D013972:Thyrotropin / Q000032:analysis; D013974:Thyroxine / Q000032:analysis
D013972:Thyrotropin; D013974:Thyroxine