Antenatal thyroid screening and childhood cognitive function.
BACKGROUND
Children born to women with low thyroid hormone levels have been reported to have decreased cognitive function.


METHODS
We conducted a randomized trial in which pregnant women at a gestation of 15 weeks 6 days or less provided blood samples for measurement of thyrotropin and free thyroxine (T(4)). Women were assigned to a screening group (in which measurements were obtained immediately) or a control group (in which serum was stored and measurements were obtained shortly after delivery). Thyrotropin levels above the 97.5th percentile, free T(4) levels below the 2.5th percentile, or both were considered a positive screening result. Women with positive findings in the screening group were assigned to 150 μg of levothyroxine per day. The primary outcome was IQ at 3 years of age in children of women with positive results, as measured by psychologists who were unaware of the group assignments.


RESULTS
Of 21,846 women who provided blood samples (at a median gestational age of 12 weeks 3 days), 390 women in the screening group and 404 in the control group tested positive. The median gestational age at the start of levothyroxine treatment was 13 weeks 3 days; treatment was adjusted as needed to achieve a target thyrotropin level of 0.1 to 1.0 mIU per liter. Among the children of women with positive results, the mean IQ scores were 99.2 and 100.0 in the screening and control groups, respectively (difference, 0.8; 95% confidence interval [CI], -1.1 to 2.6; P=0.40 by intention-to-treat analysis); the proportions of children with an IQ of less than 85 were 12.1% in the screening group and 14.1% in the control group (difference, 2.1 percentage points; 95% CI, -2.6 to 6.7; P=0.39). An on-treatment analysis showed similar results.


CONCLUSIONS
Antenatal screening (at a median gestational age of 12 weeks 3 days) and maternal treatment for hypothyroidism did not result in improved cognitive function in children at 3 years of age. (Funded by the Wellcome Trust UK and Compagnia di San Paulo, Turin; Current Controlled Trials number, ISRCTN46178175.).
Centre for Endocrine and Diabetes Sciences, Cardiff School of Medicine, Cardiff, Wales, United Kingdom. lazarus@cf.ac.uk
John H
JH
Lazarus
Jonathan P
JP
Bestwick
Sue
S
Channon
Ruth
R
Paradice
Aldo
A
Maina
Rhian
R
Rees
Elisabetta
E
Chiusano
Rhys
R
John
Varvara
V
Guaraldo
Lynne M
LM
George
Marco
M
Perona
Daniela
D
Dall'Amico
Arthur B
AB
Parkes
Mohammed
M
Joomun
Nicholas J
NJ
Wald
D002675:Child, Preschool; D005260:Female; D005865:Gestational Age; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis* / Q000188:drug therapy; D008607:Intellectual Disability / Q000175:diagnosis / Q000209:etiology; D007360:Intelligence; D007361:Intelligence Tests; D057194:Intention to Treat Analysis; D008297:Male; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis* / Q000188:drug therapy; D011262:Pregnancy Trimester, Second / Q000097:blood; D011296:Prenatal Diagnosis; D011297:Prenatal Exposure Delayed Effects / Q000175:diagnosis; D013963:Thyroid Hormones / Q000378:metabolism; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood / Q000627:therapeutic use*
D013963:Thyroid Hormones; D013972:Thyrotropin; D013974:Thyroxine