is (i v tiliiahlt' taul far thc diagnosis oj Jcltil malformations. Ttm technique is being used routinely in pregnancies carrying a high risk of externat fetal malf>rmnti(ins. Therc nrr l'en few puhlished data conierning the effect nf radiopaque dycs, conldining large amounis of iodide, on fetal thyroid function. Wc ha v c perfonned séri a i détermin a tions of sérum thyroiropin a nd thyroxine in seven newborn inf a nts to a .ssess the effect of a mniofetogra phy on feta l thyroid function. This work demomtr a les th a ï a mniofetogr a phy induces a tra nsient imp a irment of feta l thyroid function.

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SUMMARY In 327 newborns cord blood thyroxine (T4) was 118 0-4 ,ug/100 ml (SEM) (151 -9+ 5 1 nmol/l), and serum thyrotrophin (TSH) 6 7±10 ,U/ml. Variability was marked for both T4 and TSH. Remeasured in the same patients on the fifth day of life, the TSH level was 3'7 ±1-0 ,uU/ml, lower than at birth (P <0.001), while scattering of TSH values was much smaller, with 99.4% of values <12 ,uU/ml. TSH level at day 5 was therefore subsequently used as a screening procedure, considering 12 ,uU/ml as the upper limit of normal.In 14 of 1805 newborns (0-8 %), the TSH level exceeded this limit; in 3 raised TSH levels were subsequently confirmed, and hypothyroidism established by conventional criteria. One was a case of lingual thyroid (TSH >50 ,uU/ml) and the other 2 (TSH 27 and 50 ,uU/ml) iatrogenic caused by massive iodine impregnation of the mother (amniofetography). High TSH levels (160, 500, and 234 ,uU/ml) were also found in 3 hypothyroid infants aged less than one month who did not belong to the present screening programme.The striking difference between the TSH levels observed in normal and in hypothyroid infants during the first weeks of life suggests that serum TSH level at day 5 of life is the best parameter for systematic screening for congenital hypothyroidism.

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