Thyroid function tests in preterm infants born to preeclamptic mothers with placental insufficiency

Since preeclampsia causes placental insufficiency, it can be hypothesized that it decreases placental passage of thyroxine (T4) from mother to infant and thus may deepen the transient hypothyroxinemia seen in preterm infants after birth. The aim of this study was to compare thyroid function tests of preterm infants born to preeclamptic mothers with placental insufficiency with preterm infants born to mothers without placental insufficiency.

Thirty-one preterm infants born to preeclamptic mothers with placental insufficiency were included in the study (group I) and 31 preterm infants born to mothers without placental insufficiency were included as the control group (group II). Thyroid hormone levels were assayed from blood samples obtained from the women before birth and thereafter from the infants at delivery (cord) and on the 1st, 3rd, 7th, and 21st days of life.

Cord blood triiodothyronine (T3), free T3 (FT3) and free thyroxine (FT4) levels in group I were lower than in group II, whereas thyrotropin (TSH) and thyroxine binding globulin (TBG) levels were higher. No statistical difference in hormone levels studied at postnatal 1st, 3rd, 7th, and 21st day was found between the two groups.

Low levels of thyroid hormones and high level of TSH in cord blood in premature infants born to preeclamptic mothers with placental insufficiency suggest intrauterine hypothyroidism. Increase in TSH and thyroid hormone concentrations after birth reveal that the hypothalamic-pituitary-thyroid axis is intact.