Maternal TSH level and TPOAb status in early pregnancy and their relationship to the risk of gestational diabetes mellitus

Subclinical hypothyroidism is common in pregnant women and often related to adverse pregnancy outcomes, but its relationship with gestational diabetes remains controversial. In particular, the impact of thyroperoxidase antibodies status on the relationship between subclinical hypothyroidism and gestational diabetes is not clear. We investigated the association between combined thyroid stimulating hormone (TSH) level and thyroperoxidase antibodies status in early pregnancy (< 20 weeks of gestation) and gestational diabetes mellitus. A total of 7084 pregnant women met the inclusion criteria, which included thyroperoxidase antibodies-positive subclinical hypothyroidism [TSH(H)TPOAb(+)] (n = 78), thyroperoxidase antibodies-negative subclinical hypothyroidism [TSH(H)TPOAb(-)] (n = 281), thyroperoxidase antibodies-positive euthyroidism [TSH(N)TPOAb(+)] (n = 648), and thyroperoxidase antibodies-negative euthyroidism [TSH(N)TPOAb(-)] (n = 6077). Of the 7084 cases included in our study, 1141 cases were diagnosed with gestational diabetes mellitus at 24-28 weeks of pregnancy. The prevalence of gestational diabetes mellitus in TSH(N)TPOAb(-), TSH(H)TPOAb(-), TSH(N)TPOAb(+), and TSH(H)TPOAb(+) was 14.65, 19.57, 24.85, and 46.15 %, respectively. Compared with TSH(N)TPOAb(-) women, the risk of gestational diabetes mellitus was increased in all other groups of women in early pregnancy. After dividing early pregnancy into first and second trimesters, we found that TSH(H)TPOAb(-) women in the first trimester do not show this increase. Our study suggests that subclinical hypothyroidism and thyroperoxidase antibodies-positive euthyroidism in early pregnancy are associated with an increased risk of gestational diabetes mellitus.