Measuring thyroid peroxidase antibodies on the day nulliparous women present for management of miscarriage: a descriptive cohort study

BACKGROUND: There has been recent evidence suggesting the presence of anti-thyroid peroxidase antibodies (TPOAb) increases the risk of miscarriage, and levothyroxine can rescue miscarriages associated with TPOAb. We propose the most clinically pragmatic cohort to screen for TPOAb are women presenting for management of a missed miscarriage and have never birthed a liveborn. We measured serum TPOAb among nulliparous women presenting for management of miscarriage, and compared levels with women who have had 2 or more livebirths (and never miscarried). Given its potential role in immunomodulation, we also measured Vitamin D levels. METHODS: We performed a prospective descriptive cohort study at a tertiary hospital (Mercy Hospital for Women, Victoria, Australia). We measured TPOAb and Vitamin D levels in serum obtained from 118 nulliparous women presenting for management of miscarriage, and 162 controls with 2 or more livebirths (and no miscarriages). Controls were selected from a serum biobank prospectively collected in the first trimester at the same hospital. RESULTS: Nulliparous women with 1 or more miscarriages had higher thyroid peroxidase antibody (TPOAb) levels than those with 2 or more livebirths; TPOAb in miscarriage group was 0.3 mIU/L (interquartile range [IR]: 0.2-0.7) vs 0.2 mIU/L among controls (IR 0.0-0.5; p < 0.0001). We confirmed TPOAb levels were not correlated with serum human chorionic gonadotrophin (hCG) concentrations in either the miscarriage or control groups. In contrast, thyroid stimulating hormone, fT3 and fT4 levels (thyroid hormones) either trended towards a correlation, or were significantly correlated with serum hCG levels in the two groups. Of the entire cohort that was predominantly caucasian, only 12% were Vitamin D sufficient. Low Vitamin D levels were not associated with miscarriage. CONCLUSIONS: We have confirmed the association between miscarriage and increased TPOAb levels. Furthermore, it appears TPOAb levels in maternal blood are not influenced by serum hCG levels. Therefore, we propose the day nulliparous women present for management for miscarriage is a clinically relevant, and pragmatic time to screen for TPOAb.