Abstract
Aims: To compare the effects of maternal subclinical hypothyroidism (SCH) diagnosed by the 2011 or 2017 “Guidelines of the American Thyroid Association (ATA) for the diagnosis and management of thyroid disease during pregnancy and the postpartum” during the first trimester on adverse pregnancy outcomes in thyroid peroxidase antibody (TPOAb)–negative pregnant women.Methods: There were 1,556 Chinese singleton pregnant women with negative TPOAb diagnosed with either SCH or euthyroidism who were investigated, and the prevalence and risk of obstetric outcomes were compared between the two groups using 2011 and 2017 ATA standards, respectively. The effects of a mildly elevated thyroid-stimulating hormone (TSH) concentration on adverse pregnancy outcomes were evaluated by binary logistic regression.Results: Maternal SCH identified by the 2011 ATA guidelines correlated with higher rates and risks of pregnancy-induced hypertension (PIH), preeclampsia, and low-birth-weight infants, while maternal SCH diagnosed by the 2017 ATA guidelines was more likely to develop PIH, preeclampsia, cesarean delivery, preterm delivery, placenta previa, and total adverse maternal and neonatal outcomes. Moreover, a mildly elevated TSH level was significantly associated with PIH after adjustment for confounding factors.Conclusions: Compared with the 2011 ATA guidelines, the 2017 ATA guidelines could be more applicable to Chinese pregnant women to screen the effects of SCH on the majority of adverse pregnancy outcomes.
Highlights
Despite the well-known harmful effects of overt hypothyroidism on pregnancy outcomes in women at childbearing ages [1,2,3], the impacts of subclinical hypothyroidism (SCH), characterized by an elevated thyroid-stimulating hormone (TSH) with normal thyroxine, on adverse obstetric outcomes have not been yet clearly identified
Some studies indicated that SCH was associated with several obstetric complications, including preeclampsia, preterm delivery, and placental abruption [4,5,6], whereas others revealed that SCH did not result in poor pregnancy outcomes [7, 8] These inconsistencies may be mainly attributed to the differences of the diagnostic criteria for SCH in different studies
According to the 2011 American Thyroid Association (ATA) criteria, 971 women were in the ET group, and 585 women were in the SCH group, and women diagnosed with SCH had significantly lower maternal age, prepregnancy body mass index (BMI), and higher gestation age compared with those ET subjects
Summary
Despite the well-known harmful effects of overt hypothyroidism on pregnancy outcomes in women at childbearing ages [1,2,3], the impacts of subclinical hypothyroidism (SCH), characterized by an elevated thyroid-stimulating hormone (TSH) with normal thyroxine (fT4), on adverse obstetric outcomes have not been yet clearly identified. How to define SCH in pregnancy has been increasingly debated in recent years. The 2011 “Guidelines of the American Thyroid Association (ATA) for the Diagnosis and Treatment of Thyroid Disease During Pregnancy and the Postpartum” recommended that the ideal upper limit of serum TSH was 2.5 mIU/L in early pregnancy [9]. Results regarding whether a mildly elevated TSH concentration could increase adverse pregnancy outcomes have been vigorously debated [8, 13, 14]. A more liberal reference upper limit of TSH at 4.0 mIU/L in healthy pregnant women has been recommended by the 2017 ATA guidelines [15]
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