Maternal TSH levels at first trimester and subsequent spontaneous miscarriage: a nested case-control study

Area of Science:

• Reproductive Endocrinology
• Obstetrics and Gynecology
• Thyroidology

Background:

• Thyroid dysfunction is common in women of reproductive age.
• Subclinical hypothyroidism, characterized by elevated thyroid-stimulating hormone (TSH) with normal free thyroxine (FT4), is the most frequent thyroid disorder during pregnancy.
• Early pregnancy thyroid function is crucial for successful gestation.

Purpose of the Study:

• To investigate the prospective association between first-trimester thyroid function and spontaneous miscarriage.
• To determine if elevated TSH levels in early pregnancy increase miscarriage risk.

Main Methods:

• A nested case-control study was conducted, including 421 cases of spontaneous miscarriage and 1684 controls.
• Measurements included thyroid-stimulating hormone (TSH), free thyroxine (FT4), thyroid-peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb).
• Statistical analysis assessed the relationship between TSH levels and miscarriage risk, adjusting for confounding factors.

Main Results:

• Higher TSH levels were significantly associated with an increased risk of spontaneous miscarriage (OR 1.21; 95% CI, 1.13-1.30).
• Women with TSH levels of 2.5–4.87 mIU/L had a 1.47-fold increased risk of miscarriage, while those with TSH > 4.87 mIU/L had a 1.97-fold increased risk.
• These associations remained significant after controlling for TPOAb positivity and FT4 levels.

Conclusions:

• Elevated TSH levels in the first trimester are associated with a higher risk of spontaneous miscarriage.
• TSH levels between 2.5–4.87 mIU/L and above 4.87 mIU/L significantly increase miscarriage risk.
• Monitoring and managing thyroid function in early pregnancy may be important for reducing miscarriage rates.