OC11.06: Indirect MUSA features of adenomyosis are associated with reduced chances of live birth after first <i>in vitro</i> fertilization treatment

To determine the cumulative live birth rate (CLBR) after the first in vitro fertilization (IVF) treatment in women without direct features, but with or without indirect features of adenomyosis, described using the revised Morphological Uterus Sonographic Assessment (MUSA) group definitions. We included 935 women aged 25-≤39 years undergoing their first IVF/ICSI treatment between January 2019 and October 2022. The presence of indirect features of adenomyosis was confirmed by transvaginal ultrasonography prior to the first treatment. Ultrasound examinations were performed using GE Voluson 10 Expert ultrasound equipment with a 5-9 MHz transvaginal transducer. The adjusted relative risk (aRR) was evaluated using modified Poisson regression with robust error variances. Adjustments were made for age, BMI, serum antimüllerian hormone, treatment protocol, dose of follicle stimulating hormone, number of stimulation days, embryo transfer day and the presence of endometriosis. The main outcome measure was CLBR in women with or without indirect features adenomyosis. In total 188 (18.1%; 95% CI, 16.2-20.1) women had at least one indirect feature of adenomyosis, while 747 (72.0%; 95% CI, 69.3-74.8) women did not have any feature of adenomyosis. The CLBR after the first IVF treatment was lower in women with at least one indirect feature of adenomyosis [50/188, (26.6%; 95% CI, 20.3 – 32.9)] compared to women without any indirect feature, [349/747, (46.7%; 95% CI, 43.1 – 50.3)]. The crude relative risk for live birth for women with indirect features of adenomyosis compared to women without was 0.57, (95% CI, 0.45 – 0.73), p < 0.001. The aRR for CLB was 0.64 (95% CI, 0.47 – 0.87), p = 0.005. The presence of indirect MUSA features of adenomyosis indicates significantly lower chances for live birth after first IVF treatment. This is important for counselling women who seek treatment. The importance of indirect MUSA features in subfertile women should be studied further.