source: American Journal of Obstetrics & Gynecology

year: 2018

authors: Asha Rijhsinghani, Yiwen Cui

Objective:
To determine the impact of maternal and fetal thyroid-stimulating immunoglobulin (TSIG) as predictors of neonatal thyroid dysfunction in pregnancies complicated by Graves’ disease.

Study Design:
This prospective cohort study was conducted at The University of Iowa Hospital and Clinics. We analyzed all women with a history of Graves’ disease with confirmed elevated TSIG at the time they underwent cordocentesis for reasons of suspected fetal thyrotoxicosis. Indications for cordocentesis included fetal tachycardia, IUGR, oligohydramnios, hydrops, and thyromegaly. In addition, neonatal TSIG, thyroid stimulating hormone (TSH) and free T4 levels were obtained at or within 24 hours after delivery. Neonatal diagnosis of hyper/hypo-thyroidism was made based on neonatal TSH.

Results:
14 patients with history Graves’ disease were included in the study (Table 1). 7 patients were being treated for iatrogenic hypothyroidism at the time of cordocentesis. Based on blood tests, all were euthyroid with TSH levels < 3.0 mIU/L in the second trimester. Transfer of maternal TSIG to neonate appear to have a sigmoidal saturation affect (Figure 1, R2 =.69). The TSIG level from neither the mother nor the neonate corresponded to the diagnosis of neonatal thyroid dysfunction. However, the number of neonates with hyperthyroidism from mothers on levothyroxine was twice that of neonates delivered by mothers on methimazole. All neonates of the former group additionally required treatment for hyperthyroidism.

Conclusion:
While we did not find a correlation between maternal or fetal TSIG level with neonatal thyroid dysfunction, close monitoring of women with a past history of Graves’ disease and currently on levothyroxine may be warranted as they can have an increased risk for a fetus affected by hyperthyroidism.

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