Effect of Maternal Subclinical Hypothyroidism on Congenital Hypothyroidism Screening Results: A Retrospective Cohort Study

Abstract

Objectives: This study aimed to evaluate the results of congenital hypothyroidism screening (CHS) in neonates born to women with subclinical hypothyroidism (SHT) during pregnancy and to identify maternal and neonatal characteristics associated with recall rate in CHS. Material and Methods: This retrospective cohort study included non-refugee pregnant women and newborn pairs who underwent thyroid function tests during prenatal follow-up between 2014 and 2017 and had neonatal CHS records. The women were evaluated overall and divided into euthyroidism (ET) and SHT groups according to their thyroid function tests. The groups were compared in terms of CHS results. Neonates with thyroid-stimulating hormone (TSH) levels < 5.5 mIU/L were considered “normal”, while those with values ≥ 5.5 mIU/l were “recall”. Results: The antenatal thyroid function data of a total of 22383 pregnant women were analyzed. Of these, 71.6% were ET and 16.3% were diagnosed as SHT. Overall, the recall rate accounted for 5.34 % of all CHS results and the recall rate was higher in the SHT group (7.10%) compared with the ET group (5.54%) (p=0.001). Being low birth weight (LBW) or large for gestation age (LGA), maternal TSH above the 97.5th percentile, and cesarean delivery increased the risk of recall in CHS (p˂0.05). Conclusion: The recall rate was higher among the neonates of mothers with SHT. Being LBW or LGA, maternal TSH above the 97.5th percentile, and cesarean delivery increased the risk of recall in CHS.

Impact of Subclinical Hypothyroidism on Pregnancy and Newborn

“…The iodine passed from the mother to the baby plays a significant role. It is known to be mainly responsible for fetal growth and fetal neural development in the early stages of pregnancy (5). The main reason this is so important is that the developing fetus does not have the maturity to produce its free T4 (3,4).…”

The impact of hypothyroidism and levothyroxine treatment on preeclampsia risk: unraveling the connection for improved maternal and neonatal outcomes

“…2,3 Subclinical hypothyroidism is observed in 3-5% of pregnant women, whereas hypothyroidism occurs in 0.3-1% of the population. 4,5 Hypothyroidism during pregnancy is associated with an increased risk of early and late obstetric complications, such as anemia, spontaneous abortion, congestive heart failure, preeclampsia, postpartum hemorrhage, placental abnormalities, and gestational hypertension in the mother. [6][7][8] Adverse neonatal outcomes, including low birth weight, premature birth, stillbirth, and neonatal respiratory distress, may also occur.…”