Maternal Subclinical Hypothyroidism, Thyroid Autoimmunity, and the Risk of Miscarriage: A Prospective Cohort Study

Abstract

Background: Increasing data suggest that subclinical hypothyroidism (SCH) and thyroid autoimmunity (TAI) are associated with adverse pregnancy outcomes, but there are limited data on the association of these conditions in early pregnancy with subsequent miscarriage. Methods: In this prospective cohort study, we screened 3315 women at low risk for thyroid dysfunction at four to eight weeks' gestation from iodine-sufficient areas of China between January 2012 and September 2012. Thyrotropin (TSH), free thyroxine (fT4), and the autoantibodies thyroid-peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) were measured. Based on these results, women were divided into four groups for comparison: euthyroidism (ET), isolated SCH, isolated TAI (positive TPOAb or/and TgAb), and SCH with TAI (SCH + TAI). The SCH group was stratified into two subgroups (SCH 1 and SCH 2) on the basis of the level of TSH (2.5 £ TSH < 5.22 or 5.22 £ TSH < 10 respectively). Accordingly, the SCH + TAI group was also stratified into two subgroups (SCH + TAI 1 and SCH + TAI 2). The outcome of interest was miscarriage, defined as spontaneous pregnancy loss prior to 20 weeks. Results: Compared to women with ET, the risk of miscarriage was significantly higher among women with SCH 2 (7.1% vs. .28]; p = 0.000). The gestational ages of 110 women at miscarriage were lower among women with subclinical thyroid abnormalities compared to ET (11.13 -3.21 weeks with subclinical thyroid abnormalities vs. 9.33 -1.71 weeks with ET; p = 0.024). In parallel with the higher TSH levels, there were earlier gestation ages at miscarriage between subgroups of SCH and SCH + TAI (SCH 1 vs. SCH 2: 10.79 -1.77 vs. 9.70 -1.47 weeks, p = 0.039; SCH + TAI 1 vs. SCH + TAI 2: 9.59 -1.97 vs. 8.88 -1.24 weeks, p = 0.031). Conclusions: Women with SCH and TAI are at an increased risk of miscarriage between four and eight gestational weeks. Women with a combination of SCH and TAI were found to have the highest risk and earlier gestational ages of miscarriage.

Evaluation of the Clinical Features of Infertile Women With Subclinical Hypothyroidism in Relatively High-Iodine-Intake Area

“…On the other hand, in several studies, patients with positive TgAb and/or TPOAb tended to show a high miscarriage rate [12][13][14]. However, in our study, we could not observe such a tendency.…”

The course of pregnancy and its result in women who have diffuse non-toxic goiter

“…Thus, the existence of diffuse non-toxic goiter increases the possibility of spontaneous abortion more than by five times (OR 5.6 %; 95 % CI 1.3-22.9) that corresponds to the literature data [2,5,9] about the fact that dysfunction of thyroid holds the first place among the causes of pregnancy miscarriage.…”

Subclinical Hypothyroidism in Pregnancy: A Systematic Review and Meta-Analysis

“…Multiple studies have reported an association of SCH with an increase in the risk of adverse pregnancy and neonatal outcomes, including pregnancy loss, preterm delivery, gestational diabetes, gestational hypertension, preeclampsia, placental abruption, premature rupture of membranes, intrauterine growth restriction, low birth weight, small for gestational age, low Apgar score, and neonatal death (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). Furthermore, high TSH levels in women during pregnancy have been associated with an increased risk of neurocognitive deficits in the offspring (17).…”