A study of maternal subclinical thyroid abnormalities during pregnancy

Objective To study the prevalence of maternal subclinical thyroid abnormalities including subclinical hypothyroidism,isolated hypothyroxinemia and positive anti-thyroid peroxidase antibody(TPOAb) with normal thyroid function and the relationship of TPOAb and thyroid function.Methods 1 978 singleton pregnant women who took prenatal care in Beijing Haidian Maternal and Child Health Hospital were recruited in this study.Serum levels of thyroid stimulating hormone(TSH),total thyroxine(TT4),free thyroxine(FT4) and TPOAb were determined at prepartum and postpartum.Results Pregnant specific thyroid function reference ranges for the first trimester and second trimester were established by 120 women with ≤12 gestational weeks(T1 period) and 120 women with 13 to 24 gestational weeks(T2 period).82 cases(4.15%) subclinical hypothyroidism,38 cases(1.92%) isolated hypothyroxinemia,158 cases(7.99%) positive TPOAb with normal thyroid function were detected.The proportion of TSH,FT4 abnormalities in positive TPOAb group were higher than that in negative TPOAb group(15.17% vs 6.73%,P0.001;7.58% vs 4.98%,P=0.109).TPOAb level was positively related to TSH level(r=0.06,P=0.007) and negatively related to FT4 level(r=-0.02,P=0.921).Conclusion High TPOAb level is related to thyroid dysfunction.It is recommended for pregnant women with abnormal TPOAb to monitor thyroid function after delivery.