Dr. Chandan Mago, Dhawan N, Saini A, Kaur G and Pandit S
Background: Congenital Hypothyroidism (CH) is a common cause of mental retardation. Its incidence varies in different parts of the world from 1:4000 to 1:2000.
Objective: To study effect of perinatal factors on heel prick blood TSH levels and to find incidence of congenital hypothyroidism.
Study Design: Prospective Observational birth cohort study.
Method: Heel prick blood samples of total 3151babies, 1673 (53.1%) males and 1478 (46.9%) females was taken on special graded filter paper within 48 hours of life and screened by fluoroimmunometric assay. Babies with TSH value more than 9µU/ml were recalled at 5 to 7 days of life for repeat sample of T3, T4, TSH. Babies with low T4 less than 7 µgm/dl and TSH more than 20 µU/ml were labelled as congenital hypothyroidism. The effect of perinatal factors was analyzed statistically.
Result: In our study, thyroid screening in two third of neonates was done at 12 to 24 hours of age. Median (IQR) TSH of 3151 neonates was 3(1.4-5.5) µU/ml. TSH level was significantly low in neonates with sampling at age of >24 hours. Recall rate in our study was 7.6% (238 cases) and 2 neonates were diagnosed as congenital hypothyroidism. Neonates with assisted deliveries showed a higher median (IQR) TSH level 5.3(3-9.1µU/ml) as compared to normal vaginal deliveries and lower segment caesarean section. This was statistically significant (p<0.001). Neonates with perinatal asphyxia had higher median (IQR) TSH values 8.2(1.7-12.5) µU/ml and this was statistically significant.
Conclusions: Incidence of congenital hypothyroidism in our study was 1:1575. TSH levels were high in neonates with assisted delivery and perinatal asphyxia. TSH level was low in neonates delivered by caesarean section. There was no effect of birth weight, sex and gestational age on neonatal TSH level.
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