Impact of subclinical hypothyroidism on the outcome of pregnancy

Abstract

Objective To evaluate the impact of subclinical hypothyroidism(SCH)on the outcome of pregnancy and the therapeutic effect of L-T4. Methods A total of 1 786 pregnant women during the first, second, and third trimesters were enrolled for thyroid screening by determining serum free thyroxine(FT4), total thyroxine(TT4), thyrotropin(TSH), and thyroid peroxidase antibody; 123 pregnant women with SCH were successfully divided into treated group(n=42)and untreated group(n=81). The treated group was treated by L-T4 based on American Thyroid Association(ATA) 2011 guideline. Collected items include obstetric outcomes and complications. Results (1)Compared to control group, the rate of spontaneous abortion in pregnant women during first trimesters was increased in SCH group(20.99% vs 8.45%, χ2=12.96, P=0.00), with higher incidence of diabetes during second trimester(24.69% vs 10.45%, χ2=14.11, P=0.00). The incidences of hypertension during pregnancy, premature delivery, ablatio placentae, placenta praevia, fetus growth restriction, and low birth weight showed no difference between two groups(all P>0.05). (2)Compared with the untreated group, the incidences of spontaneous abortion and diabetes were decreased in the treated group(7.14% vs 20.99%, χ2=3.89, P=0.05; 9.52% vs 24.69%, χ2=4.05, P=0.04), while the incidences of hypertension, premature delivery, ablatio placentae, placenta praevia, fetus growth restriction, and low birth weight infant accident rate were not different between two groups(all P>0.05). Conclusions SCH during the frist trimester is a risk factor of spontaneous abortion; SCH during the middle stage of pregnancy is a risk factor of gestational diabetes mellitus. Treatment of SCH with L-T4 may be beneficial. (Chin J Endocrinol Metab, 2015, 31: 937-940) Key words: Pregnancy; Subclinical hypothyroidism; Pregnant outcome