Urinary iodide levels in term newborns and their mothers--a pilot study.

Although the Philippines is considered an iodine-deficient country, there are no documented iodine deficiency disorders (IDD) among newborns screened to be positive for congenital hypothyroidism. The objectives of this pilot study were: (1) to determine the levels of urinary iodide (UI) in normal term newborns and their mothers, and (2) to correlate the UI levels of newborns with that of their mothers. This study included 44 pairs of full term newborns and their mothers who delivered at two hospitals in Manila last July 2001. UI determination by the Rapid Urinary Iodide Test was done during the first 24 hours after delivery. Results showed that eighteen percent (8/44) of the neonates were iodine deficient (<10 microg/dl), 71% (31/44) had adequate UI levels (>10-30microg/dl) and 11% (5/44) had high UI levels (>30microg/dl). None of the mothers had deficient UI levels. Among the neonates who had deficient UI levels, 50% (4/8) of the mothers had adequate UI levels and the other half (4/8) had high levels. Among the neonates who had adequate UI levels, most mothers had high UI levels (22/31 or 71%) and the rest (9/31 or 29%) had adequate UI. All newborns with high UI levels had mothers with high UI levels. Screening for Congenital Hypothyroidism was negative in all the neonates who underwent newborn screening (39/44). In conclusion, most term neonates (82%) had adequate to high UI levels, and 18% had deficient UI levels despite adequate maternal levels. In case of low UI level, repeat determination is advised. If the level remains low, newborn screening using TSH is useful to rule out hypothyroidism. A bigger multicenter study to determine the incidence of IDD in neonates and infants is recommended.