title: The effect of maternal subclinical hypothyroidism on IQ in 7- to 8-year-old children: A case-control review.
abstract: BACKGROUND
  In Ireland, pregnant women are not routinely screened for subclinical hypothyroidism (SCH).
  
  
  OBJECTIVE
  Our objective was to compare the intelligence quotient (IQ) of children whose mothers had been diagnosed with SCH prenatally with matched controls using a case-control retrospective study.
  
  
  METHODS
  In a previous study from our group, 1000 healthy nulliparous women were screened anonymously for SCH. This was a laboratory diagnosis involving elevated TSH with normal fT4 or normal TSH with hypothyroxinaemia. We identified 23 cases who agreed to participate. These were matched with 47 controls. All children underwent neurodevelopmental assessment at age 7-8. Wechsler Intelligence Scale for Children IV assessment scores were used to compare the groups. Our main outcome measure was to identify whether there was a difference in IQ between the groups.
  
  
  RESULTS
  From the cohort of cases, 23 mothers agreed to the assessment of their children as well as 47 controls. The children in the control group had higher mean scores than those in the case group across Verbal Comprehension Intelligence, Perceptual Reasoning Intelligence, Working Memory Intelligence, Processing Speed Intelligence and Full Scale IQ. Mann-Whitney U-test confirmed a significant difference in IQ between the cases (composite score 103.87) and the controls (composite score 109.11) with a 95% confidence interval (0.144, 10.330).
  
  
  CONCLUSIONS
  Our results highlight significant differences in IQ of children of mothers who had unrecognised SCH during pregnancy. While our study size and design prevents us from making statements on causation, our data suggest significant potential public health implications for routine prenatal screening.
authors.affiliation: Department of Obstetrics & Gynaecology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Niamh C
authors.initials: NC
authors.lastname: Murphy
authors.affiliation: Department of Obstetrics & Gynaecology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Mairead M
authors.initials: MM
authors.lastname: Diviney
authors.affiliation: Department of Obstetrics & Gynaecology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Donnelly
authors.affiliation: Department of Obstetrics & Gynaecology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Cooley
authors.affiliation: Department of Statistics, Rotunda Hospital, Dublin, Ireland.
authors.forename: Colin H
authors.initials: CH
authors.lastname: Kirkham
authors.affiliation: Department of Neonatology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Adrienne M
authors.initials: AM
authors.lastname: Foran
authors.affiliation: Department of Obstetrics & Gynaecology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Fionnuala M
authors.initials: FM
authors.lastname: Breathnach
authors.affiliation: Department of Obstetrics & Gynaecology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Fergal D
authors.initials: FD
authors.lastname: Malone
authors.affiliation: Department of Obstetrics & Gynaecology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Geary
mesh_terms: D000328:Adult; D017677:Age Distribution; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications / Q000175:diagnosis*; D008607:Intellectual Disability / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D007361:Intelligence Tests; D007494:Ireland / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D009483:Neuropsychological Tests; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis*; D011296:Prenatal Diagnosis; D015995:Prevalence; D011379:Prognosis; D012016:Reference Values; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution
keywords: intelligence quotient; screening; subclinical hypothyroidism