The effect of maternal iodine status on infant outcomes in an iodine-deficient Indian population.
BACKGROUND
An adequate intake of iodine during pregnancy is essential for the synthesis of maternal thyroid hormones needed to support normal fetal development. This study aimed to assess the iodine status of pregnant tribal Indian women and their infants and to determine the impact of maternal iodine status on infant growth and behavior.


METHODS
A prospective, observational study was undertaken to assess the iodine status of tribal pregnant Indian women living in Ramtek, northeast of Nagpur, India. Pregnant women were recruited at 13-22 weeks gestation (n=220), visited a second time at 33-37 weeks gestation (n=183), and again visited at 2-4 weeks postpartum with their infants. Sociodemographic, anthropometric, and biochemical data, including household salt, blood, and urine samples were obtained from pregnant women. Urine samples, anthropometric, and neonatal behavioral data were collected from infants.


RESULTS
The median urinary iodine concentration (MUIC) at recruitment (mean gestation=17.5 weeks) of mothers was 106 μg/L, which declined to 71 μg/L at the second visit (mean gestation=34.5 weeks) similar to the postpartum MUIC of 69 μg/L, indicating that these women were iodine deficient. Infant (mean age=2.5 weeks) MUIC was 168 μg/L. Median maternal thyroid stimulating hormone (TSH) and free thyroxine (FT(4)) concentrations at first and second visits were 1.71 and 1.79 mIU/L and 14.4 and 15.4 pmol/L, respectively; 20.0% of women at first visit had TSH >97.5th percentile and 1.4% had FT(4) <2.5th percentile. Salt iodine concentration was a significant predictor of maternal UIC (p<0.001), and postpartum maternal UIC was a significant predictor of infant UIC (p<0.001). For every pmol/L increase in maternal FT(4) concentration at first visit, both infant weight-for-age Z-score and length-for-age Z-score increased by 0.05 units. There was no relationship between maternal UIC, FT(4), or TSH at first visit and neonatal behavior.


CONCLUSIONS
Despite three quarters of the women in this study having access to adequately iodized salt (i.e., >15 ppm), these pregnant tribal Indian women were iodine deficient. Increasing the iodine content of salt deemed adequately iodized and iodine supplementation are two strategies that might improve the iodine status of these pregnant women and, consequently, the growth of their infants.
Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
Kavitha C
KC
Menon
Sheila A
SA
Skeaff
Christine D
CD
Thomson
Andrew R
AR
Gray
Elaine L
EL
Ferguson
Sanjay
S
Zodpey
Abhay
A
Saraf
Prabir Kumar
PK
Das
Chandrakant S
CS
Pandav
D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001827:Body Height; D001835:Body Weight; D002657:Child Development; D004032:Diet; D005260:Female; D005865:Gestational Age; D006801:Humans; D007194:India; D018730:Infant Behavior; D007231:Infant, Newborn; D007455:Iodine / Q000008:administration & dosage / Q000172:deficiency* / Q000652:urine; D016014:Linear Models; D008137:Longitudinal Studies; D015999:Multivariate Analysis; D009752:Nutritional Status; D011247:Pregnancy; D011248:Pregnancy Complications / Q000209:etiology* / Q000652:urine; D011297:Prenatal Exposure Delayed Effects; D039401:Prenatal Nutritional Physiological Phenomena; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D055815:Young Adult
D015415:Biomarkers; D013972:Thyrotropin; D007455:Iodine; D013974:Thyroxine