Association between thyroid function in the first trimester in twin pregnancies and gestational diabetes mellitus / 中华围产医学杂志

ABSTRACT

Objective:To explore the associations between thyroid function in the first trimester in twin pregnancies and gestational diabetes mellitus (GDM) and the risk factors of twin pregnancies complicated by GDM.Methods:Retrospective analysis was performed on 745 twin pregnancies delivered after 28 weeks at the Third Affiliated Hospital of Sun Yat-sen University from January 2015 to December 2021, and they were divided into GDM group ( n=186) and the control (non-GDM) group ( n=559). Thyroid dysfunction was diagnosed based on the reference range of singleton and twin pregnancies recommended by the Guideline on diagnosis and management of thyroid diseases (2nd edition) in China and the literature, respectively. Independent sample t-test, Chi-square test, or Fisher exact test, and Mann-Whitney U test were used to compare the general clinical characteristics and thyroid function between the two groups. Spearman rank correlation analysis was performed to analyze the correlation between free thyroxine (FT 4), thyroid stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), and fasting plasma glucose (FPG) in the first trimester as well as glucose levels in 75 g oral glucose tolerance test (OGTT). The associations between FT 4, TSH at different levels, and the detection rate of GDM, and the risk factors of GDM in twin pregnancies were analyzed using logistic regression. Results:(1) The prevalence of GDM in twin pregnancies was 25.0% (186/745). The positive rate of TPOAb was 13.6% (101/745). FPG in the first trimester was higher in the GDM group than that in the control [(4.7±0.5) vs (4.5±0.4) mmol/L, t=－5.08, P<0.001]. (2) No correlation between FT 4, TSH levels, the positive rate of TPOAb in the first trimester and FPG in the first trimester as well as OGTT results was found (all P>0.05). (3) There was no significant difference when using the thyroid function reference range for twin or singleton pregnancy in detecting hypothyroidism [0.5% (4/745) vs 0.4% (3/745)] and subclinical hypothyroidism [1.2% (9/745) vs 1.3% (10/745)] among the included subjects (both P>0.05), however, there were significant differences in the detection rates of hypothyroxinemia alone [25.0% (186/745) vs 12.9% (96/745)], hyperthyroidism [2.4% (18/745) vs 12.9% (96/745)] and subclinical hyperthyroidism [5.8% (43/745) vs 12.1% (90/745)]( χ2 were 35.43, 33.43 and 18.24, all P<0.001). There was no significant difference in the detection rate of thyroid disease between the GDM and control groups (all P>0.05). (4) FT 4 and TSH levels were grouped into quartiles ( Q1, Q2, Q3, and Q4), which showed that the detection rate of GDM was the highest [27.8% (52/187)] in women with FT 4 in Q1 and was the lowest [23.0% (43/187)] in those with FT 4 in Q2. However, the detection rate was the lowest in women with TSH in Q1 [24.1% (45/187)] and was the highest [27.4%(51/186)] in those with TSH in Q4. Taking Q1 of FT 4 and TSH as a reference, the logistic regression model showed that there were no statistically significant differences between FT 4, TSH at different levels, and GDM, even after adjusting for age, preconception-body mass index (pre-BMI), family history of diabetes, mode of conception, and chorionicity (all P>0.05). (5) Multivariate logistic regression analysis showed that maternal age ( OR=1.10, 95% CI 1.05-1.15), pre-BMI ( OR=1.13, 95% CI 1.07-1.21), family history of diabetes ( OR=2.73, 95% CI 1.53-4.85), and FPG in the first trimester ( OR=2.14, 95% CI 1.38-3.32) were independent risk factors for twin pregnancies complicated by GDM. Conclusions:Twin pregnant women with higher maternal age, pre-BMI, FPG in the first trimester and family history of diabetes were at higher risk of GDM. No significant correlation is found between maternal thyroid function in the first trimester and GDM in twin pregnancies.