Right Ventricular-Specific Fetal Cardiac Remodeling Associated with Maternal Thyroid Pathology

To evaluate the association between maternal thyroid pathology and second-trimester fetal cardiac morphometry, with prespecified focus on left ventricular (LV) and right ventricular (RV) sphericity indices.

This single-center retrospective cohort study included pregnant women who underwent first-trimester thyroid function testing (11 + 0-13 + 6 weeks) and standardized fetal cardiac morphometry at 20 + 0-22 + 6 weeks. Women with overt or subclinical hypothyroidism, overt or subclinical hyperthyroidism, or euthyroid thyroid autoimmunity (n = 175) were compared with gestational-age-matched controls (n = 175). Multivariable regression evaluated independent associations after adjustment for maternal age, body mass index, gestational age, and levothyroxine use.

RV sphericity index was significantly lower in the thyroid pathology group than in controls (1.63 ± 0.08 versus 1.71 ± 0.09, p < .001), whereas LV sphericity index did not differ. Interventricular septal thickness was greater (2.06 ± 0.12 versus 1.96 ± 0.14 mm, p < .001), and global cardiac sphericity index was lower (p < .001). Similar findings were observed across hypothyroidism, hyperthyroidism, and euthyroid thyroid autoimmunity. RV sphericity index showed the greatest discriminative performance (area under the curve 0.791). Thyroid pathology remained independently associated with RV sphericity index and interventricular septal thickness. Composite adverse perinatal outcome was more frequent in the thyroid pathology group (12.2% versus 5.1%, p = .023).

Maternal thyroid pathology was associated with subtle RV-specific fetal cardiac remodeling characterized by reduced RV sphericity and increased interventricular septal thickness, without significant LV involvement. Similar findings across all thyroid subgroups suggest that fetal cardiac remodeling may accompany a broad spectrum of maternal thyroid disorders. RV sphericity index may represent a promising imaging marker, although prospective external validation is required before clinical application.