Cord blood thyroid stimulating hormone level--interpretation in light of perinatal factors.

OBJECTIVE To study the influence of perinatal factors on cord blood TSH (CB TSH) levels. DESIGN Cross-sectional study. SETTING Tertiary care private hospital. METHODS CB TSH levels were measured in 952 live-born infants using electrochemiluminescence immunoassay. The effect of perinatal factors on the CB TSH levels was analyzed statistically. RESULTS The median CB TSH was 8.75 microIU/mL (IQR = 6.475 -12.82) with 11.5% neonates having values more than 20. CB TSH was significantly raised in first order neonates (P <0.01) and in babies delivered by assisted vaginal delivery and normal delivery (P <0.01). Neonates who had fetal distress or non-progress of labour had significantly higher CB TSH than those who were delivered by elective caesarean section. Requirement of resuscitation beyond the initial steps and low Apgar scores at 1 minute also resulted in significantly raised CB TSH (both P <0.01). Maternal hypothyroidism, maternal hypertension and neonates weight appropriateness for gestation, gestational age and birth weight did not have significant effect. CONCLUSIONS The incidence of high cord blood TSH (>20 microU/mL) is 11.45%. On multivariate analysis, requirement of resuscitation, mode of delivery and fetal distress as indication for LSCS were significant factors affecting CB TSH values. Hence, these values need to be interpreted in light of perinatal factors.