Relationship Between BDNF Content In Cord Blood And Early Neurobehavior In Newborns With Subclinical Hypothyroidism During Pregnancy

Objective: The mechanism of neonatal neurobehavioral abnormalities in patients with subclinical hypothyroidism(SCH)during pregnancy is unclear.Although some studies have shown that brain-derived neurotrophic factor(BDNF)plays a key role in neurobehavior,the relationship between cord blood BDNF level and neurobehavior in neonates with gestational SCH has not been reported.Therefore,this study is to explore whether the change of serum BDNF level is related to the early neurobehavioral abnormalities of neonates with gestational SCH.Methods: In this study,72 patients with gestational SCH and 76 healthy controls(HC)were included.The general data of Body Mass Index(BMI),the number of pregnancies,thyroid function in the early,middle and late stages of pregnancy,labor process,newborn birth weight and so on of all subjects were collected,and the neonatal neurobehavioral ability was evaluated by NBNA.The level of BDNF in neonatal cord blood was determined by Elis method.Results: 1.General information: There was no significant difference between patients with SCH during pregnancy and the control group in terms of age,maternal and childbirth times,total stage of labor,fetal weight,fetal sex,production mode,etc.(P>0.05).The differences between gestational age,preconceptional BMI,prenatal BMI,first stage of labour,and second stage of labour were statistically significant(Ps<0.05).The hypothyroid group had a smaller gestational age than the control group,a higher BMI before pregnancy and BMI before delivery,and a longer duration of the first and second stages of labour than the control group.2.Comparison of thyroid function between experimental group and control group: The difference in thyroid function between patients with SCH during pregnancy and normal control in the first,middle and third trimester of pregnancy was statistically significant.The TSH level in the first trimester and third trimester was higher than that in control group(Ps<0.001),the level of TPOAb in the third trimester was higher than that in the control group(Z=-2.878,P<0.01),and the TSH level was higher(Z=-5.925,P<0.001).There was no significant difference in the remaining thyroid function levels.3.Comparison of neonatal neurobehavioral score and umbilical cord blood BDNF between the two groups: the total score of neonatal NBNA score,behavioral ability,passive muscle tension,active muscle tension,primitive reflex,general estimation and the level of BDNF in cord blood in newborns with SCH during pregnancy was lower than that in the control group(P<0.05).4.Correlation between neonatal umbilical cord blood BDNF and thyroid function and neurobehavioral ability during pregnancy: neonatal umbilical cord blood BDNF of pregnant patients with SCH was negatively correlated with TSH in early pregnancy(r=-0.346,P<0.01),and was not related to thyroid function in the second and third trimester of pregnancy.In terms of neurobehavior,neonatal cord blood BDNF of pregnant patients with SCH was positively correlated with the total score of NBNA(r=0.563,P<0.001),behavioral ability(r=0.455,P<0.001),active muscle tension(r=0.518,P<0.001)and general assessment(r=0.348,P<0.01)within 3 days.There was no significant correlation with the passive muscle tone and the primary reflex of the newborn.Further multiple linear regression found that BDNF level and NBNA total score in patients with SCH(β=0.492,P<0.001),behavioral ability(β= 0.270,P<0.05),active muscle tension(β= 0.509,P<0.001),general evaluation(β=0.374,P<0.01),TSH level and NBNA total score(β=-0.215,P<0.05)and behavioral ability(β=-0.378,P<0.01).Conclusion: Early neonatal neurobehavioral capacity is reduced in patients with SCH during pregnancy and is associated with BDNF levels in cord blood.