Chapter 5 : Transient hypothyroxinemia in severe hypertensive disorders of pregnancy

Objective: Assess whether and to what extent thyroid function is affected in pregnant women with early and severe hypertensive disorders and their newborns. Methods: Patients were 80 women with preeclampsia, hemolysis, elevated liver enzymes and low platelet count syndrome or gestational hypertension combined with fetal growth restriction in the 24th to 34th week of singleton pregnancies. Maternal thyroid hormone levels and thyroid peroxidase antibodies (TPOab) were determined at admission and three months post term. Neonatal levels were determined from cord blood at delivery. Maternal hypothyroxinemia was defined as fT4 value below 9 pmol/l. Results: At admission 26 (33%) women in the Study Group had fT4 levels below 9 pmol/l, with spontaneous normalization during pregnancy. There were, however, no statistically significant differences between thyroid hormone values in women in the study group compared to 10 normotensive pregnant women in their third trimester. Three months post term 97.5% of patients had thyroid hormone levels in the normal range. TPOab were elevated in 10% of women post partum. Their infants, born at a median gestational age of 30/7 weeks, had lower cord blood fT4 and TSH values compared to preterm infants of the comparison group, appropriate for gestational age. Cord blood fT4 had no correlation with gestational age or maternal fT4, but there was a significant correlation of cord blood fT4 with umbilical artery pH. Conclusion: Women with severe hypertensive disorders of pregnancy may have transiently lower fT4 levels, without evidence of a thyroid disorder. Their neonates have lower fT4 levels at birth unrelated to maternal fT4, but related to prenatal acidosis. Buimer Final 6 mei .indd 84 13/05/2008 21:49:46 85 Preeclampsia and Thyroid Hormone Levels