Thyroglobulin in cord blood. The influence of the mode of delivery and the smoking habits of the mother.

The cord thyroglobulin (Tg) concentration was estimated in 160 full-term newborns of whom 103 were delivered normally, 26 by elective Cesarean section and 31 by vacuum extraction. There was no correlation between the median cord Tg concentration and gestational age at delivery (37-43 weeks), birth weight or sex of the child or the median cord TSH concentration. The median cord Tg concentration was significantly higher in the children born by Cesarean section than in those delivered by vacuum extraction (P less than 0.001). The same tendency was found when smokers and non-smokers were compared separately. Mechanical force on the thyroid gland during labour and delivery therefore does not seem to increase the cord Tg concentration. The influence of maternal cigarette smoking on the cord Tg concentration was studied also. Forty-five mothers were smokers. The median cord Tg concentration in the children of these women was significantly higher than in the children of non-smoking mothers (130 micrograms/l vs 100 micrograms/l, P less than 0.001), whereas the median cord TSH concentration did not differ between these groups. It therefore seems possible that components of cigarette smoke, e.g. thiocyanate, may have a direct effect on the thyroid gland of the fetus.