Anti-TPO-Negative Subclinical Hypothyroidism in the First Trimester and Its Influences on Obstetric and Neonatal Outcomes

The aim of this study was to assess the relationship between maternal anti-thyroid peroxidase (anti-TPO)-negative subclinical hypothyroidism (SCH) in the first trimester with complications of pregnancy and neonatal outcomes.The study was done at a maternity and children's research training hospital. First-trimester thyroid function tests (TFTs) (free thyroxine (FT4), thyroid stimulating hormone (TSH), anti-TPO) were checked for mothers who gave birth at the center, and their newborns were accepted for the study. Based on the results of the TFTs, two groups were formed, the normal thyroid function (euthyroid) and SCH groups. The neonatal and maternal outcomes were noted. This study included 150 mothers, of whom 110 (73.3%) had normal thyroid function and 40 (26.7%) had anti-TPO-negative subclinical hypothyroidism (SCH). Based on thyroid function tests (TSH: 0.1-4.0 mIU/L, FT4: 0.7-1.8 ng/dL), significant differences in pregnancy complications wereobserved, with higher rates of placental abruption, preeclampsia, and postpartum hemorrhage in the SCH group (p<0.001). Neonatal outcomes in the SCH group showed significantly higher rates of small for gestational age (SGA) (52.5%), NICU admission (77.5%), low Apgar score (52.5%), and transient tachypnea of the newborn (TTN) (67.5%) (all p<0.001). Logistic regression analysis identified SCH as a significant risk factor for TTN (OR=7.24; 95% CI: 3-17; p<0.001), while no significant associations were found with gestational age (p=0.194) or maternal age (p=0.600). Anti-TPO-negative SCH in pregnancy has undesirable effects, not only during pregnancy but also in siblings, and surprisingly, it may be a risk factor for TTN.