Thyroid ultrasonic changes relate to implantation failure in euthyroid women with thyroid autoimmunity undergoing in vitro fertilization/intracytoplasmic sperm injection.

Objective: To determine whether ultrasonic manifestations of Hashimoto's thyroiditis (HT) related to embryo qualities or pregnancy outcomes in women with thyroid autoimmunity (TAI) undergoing in vitro fertilization/intracytoplasmic sperm injection.

Methods: Our study was a retrospective cohort study. A total of 589 euthyroid women enrolled from January 2017 to December 2019. 214 TAI women and 375 control women were allocated in each group according to serum levels of thyroid peroxidase antibodies (TPOAb) and/or anti-thyroglobulin antibodies (TgAb). Basal serum hormone levels and thyroid ultrasound were assessed, embryo qualities, pregnancy outcomes were collected from medical records. Diagnosis of thyroid ultrasound was used for subanalysis. Logistic regression was used to evaluate outcomes of embryo development and pregnancy.

Results: Implantation rate was significantly lower in euthyroid women with TAI compared with control group (TAI group: 65.5% vs. Control group: 73.0%, adjusted OR (95% CI): 0.65 (0.44, 0.97), p = 0.04). We further stratified TAI group into two groups: one group with HT features under ultrasound and another group with normal thyroid ultrasound. After regression analysis, TAI women with HT morphological changes had a lower chance of implantation compared with control group (TAI group with HT: 64.1% vs. Control group: 73.0%, adjusted OR (95% CI): 0.63 (0.41, 0.99), p = 0.04), while there was no significant difference on implantation rate between TAI women with normal thyroid ultrasound and control group. Other outcomes, such as embryo qualities and pregnancy rate, were comparable between TAI and control groups.

Conclusions: A higher risk of implantation failure was seen among euthyroid women with TAI, especially women with HT morphological changes under ultrasound. The underlying mechanisms of implantation failure among euthyroid HT patients need further research.