Effect of maternal and neonatal factors on cord blood thyroid stimulating hormone

Abstract

Background:Congenital hypothyroidism (CH) is most common preventable cause of mental retardation in children. Cord blood Thyroid Stimulating Hormone (CBTSH) level is an accepted screening tool for CH.Objectives:To study CBTSH profile in neonates born at tertiary care referral center and to analyze the influence of maternal and neonatal factors on their levels.Design:Cross retrospective sectional study.Methods:Study population included 979 neonates (males = 506 to females = 473). The CBTSH levels were estimated using electrochemiluminescence immunoassay on Cobas analyzer. Kit based cut-offs of TSH level were used for analysis. All neonates with abnormal CBSTH levels, were started on levothyroxine supplementation 10 μg/Kg/day and TSH levels were reassessed as per departmental protocol.Results:The mean CBTSH was 7.82 μIU/mL (Range 0.112 to 81.4, SD = 5.48). The mean CBTSH level was significantly higher in first order neonates, neonates delivered by assisted vaginal delivery and normal delivery, delivered at term or preterm, neonates with APGAR score <5 and those needing advanced resuscitation after birth. The CBTSH level >16.10 and <1.0 μIU/mL was found in 4.39 % and 1.02 % neonates respectively. The prevalence rate of CBTSH level >16.1 μIU/mL was significantly higher in neonates delivered by assisted vaginal delivery and normal delivery, term and preterm neonates, APAGR score of <5, presence of fetal distress, need for resuscitation beyond initial steps and in those with birth weight of <1.5 Kg. Three neonates were confirmed to have CH after retesting of TSH level.Conclusions:The CBTSH estimation is an easy, non-invasive method for screening for CH. The cutoff level of CB TSH (μIU/mL) >16.10 and <1.0 led to a recall of 5.41% of neonates which is practicable given the scenario in our Country. The mode of delivery and perinatal stress factors have a significant impact on CBTSH levels and any rise to be seen in the light of these factors. The prevalence rate of CH after recall was ~3 in 1000 live births.

Perinatal factors associated with neonatal thyroid-stimulating hormone in normal newborns

“…We did not find any significant differences in TSH level according to sex, in line with many previous studies 6 8 12 13 15 21 22) . However, a few studies have reported higher TSH levels in boys 7 14) .…”

“…There was no relationship between TSH level and maternal age in our study, in line with most previous studies 6 7 8 12 13) . Only one study has reported a positive relationship between maternal age and TSH level 22) .…”

“…Maternal disease such as overt and gestational diabetes, essential or pregnancy-induced hypertension, and hyper- or hypothyroidism did not affect TSH levels, in agreement with many previous studies 6 7 8 12 14) and in disagreement with one study in which the authors reported an increased TSH level in maternal diabetes and preeclampsia 5) . In addition, the use of medications to mothers did not affect TSH levels in our study.…”

“…Previous studies have reported that TSH levels in cord blood are higher in infants born through vaginal delivery than in those born through cesarean section 5 6 10 11 12 13) , and higher in those born through vacuum-assisted delivery than in those born through spontaneous vaginal delivery 6 10 14) . Our results support these studies, although we investigated capillary blood TSH, not cord blood TSH, and infants born through cesarean section were excluded.…”

“…Many studies have reported that first babies have higher TSH levels than subsequent babies 6 7 12 14) . In contrast, one study from Belgium (where iodine insufficiency is common) reported no differences in TSH level according to birth order 8) .…”