Iodization and thyroid status in relation to stillbirths and congenital anomalies.

Thyroid status is known to have an important bearing on the ability of a woman to conceive, and to bring a normal infant to term. Thyroid status has changed in a number of previously iodine deficient countries as a result of recent iodization programmes. In this study, examination has been made of changes in the rates of two pregnancy outcomes in Tasmania, a State of Australia, namely, stillbirth and infant death due to congenital anomalies. Tasmania began iodine supplementation in 1950. Stillbirth rates declined more rapidly than in Australia as a whole, but show a peak associated with the peak of iodine-induced thyrotoxicosis in 1966. Congenital anomalies causing death show an initial rise in the early 1950s. It is suggested that this is due to persistence of iodine deficiency in the foetus after maternal iodine status improved sufficiently to allow term delivery of a live infant. The later fall coincides with the reaching of reproductive age by the first cohort of Tasmanian women who had been iodine sufficient since childhood, who would therefore not deprive their own foetus of iodine. Examination of trends in New Zealand, Switzerland and Finland, which have each introduced iodization programmes, confirms the largely beneficial effect of iodine supplementation on the rate of infant death due to congenital anomalies.