Changes in iodine metabolism during late pregnancy and lactation: a longitudinal study among Sudanese women

To elucidate the persistence, or otherwise, of the pregnancy-related changes in the iodine metabolism and thyroid function in a population residing in an area of mild iodine deficiency in the Sudan. A longitudinal prospective cohort study involving pregnant women who were recruited during their third trimester of pregnancy and were followed up for up to nine months after delivery. The study was conducted among Sudanese women residing in the Omdurman area in Khartoum, an area with a total goitre rate of 17.5%. Forty-seven pregnant women were recruited during their third trimester of pregnancy. Their mean age and weight were 29+/-4.6 y and 62.4+/-8.7 kg, respectively. Age matched healthy non-pregnant women living in the same area (n=40) served as a control group. Serum levels of thyrotropin (TSH), thyroxine (T4), triiodothyronine (T3), thyroglobulin (Tg) and the urinary iodine concentration (UIC) were determined during the third trimester (first occasion), and subsequently at three months (second occasion), six months (third occasion) and nine months after delivery (fourth occasion). Control subjects provided corresponding samples on one occasion. UIC, TSH, Tg, FT4 and T3. During the third trimester of pregnancy the median UIC and the free T4 (FT4) were lower than in the control group (P