Isolated Maternal Hypothyroxinemia and Its Perinatal Outcome in North Macedonia

Abstract

Isolated maternal hypothyroxinemia (IMH) is defined as the presence of low maternal total thyroxine (TT4) level in conjunction with normal maternal thyroid-stimulating hormone (TSH) level. The aim was to investigate whether IMH is associated with adverse pregnancy outcome in North Macedonia. Dried blood spot samples were obtained from 359 pregnant women meeting the inclusion criteria and analyzed for TT4 and TSH. Postpartum data were entered from their medical histories. Out of 359 women, 131 (37.42%) belonged to IMH group. There were statistically significant differences in birth weight (p=0.043), intrauterine growth restriction (IUGR) (p=0.028), Apgar score at 1 min <7 (p=0.018) and cesarean section for dystocia/disproportion (p=0.024) between the IMH and normal thyroid function (NTF) groups. In regression analysis, TSH was a significant variable predicting Apgar score (βst=0.05597, p=0.047), body mass index predicting birth weight (βst=0.02338, p=0.045) and TT4 predicting small for gestational age/IUGR (βst=-0.089834, p=0.029) in IMH group. TT4 was a strong predictor of birth weight (βst=-0.004778, p=0.003) and premature delivery (βst=0.028112, p=0.004) in NTF group. The impact of IMH in pregnancy remains controversial. IMH was associated with an increased maternal BMI and higher birth weight of neonates. Overweight could be a potential risk factor for thyroid dysfunction in pregnant women, and specifically IMH. The worst fetal outcome was seen in IMH mothers examined in second trimester. We found TSH, TT4 and BMI to be strong predictors of perinatal outcomes.

Keywords

• Isolated hypothyroxinemia
• Perinatal outcome
• Low birth weight
• Preterm birth
• Obesity