Uterine artery S/D ratio and serum CA125 as predictors of early pregnancy loss in women with ovarian endometriomas: a retrospective case-control study

Endometriosis affects approximately 10% of women of reproductive age and is associated with increased risks of infertility and miscarriage. Although the spontaneous miscarriage rate in women with endometriosis is higher than in the general population, specific risk factors and predictive markers for early pregnancy loss in this population remain poorly understood, particularly for women with smaller endometriomas who achieve natural conception. This study aimed to investigate risk factors for early spontaneous miscarriage in women with endometriosis with natural conception and evaluate the predictive value of uterine artery blood flow parameters and serum CA125 levels.

This retrospective case-control study was conducted at the Fujian Maternity and Child Health Hospital and included 209 women with ovarian endometriomas smaller than 4 cm who achieved natural conception and intrauterine pregnancy between January 2022 and June 2024. Patients were divided into spontaneous miscarriage group (n = 61, 29.19%) and non-miscarriage group (n = 148, 70.81%) based on early pregnancy outcomes. All patients underwent follicular monitoring, endometrial assessment, and uterine artery blood flow evaluation starting from cycle days 9-10. All patients received uniform luteal support with dydrogesterone (20 mg daily from post-ovulation until 10 weeks of gestation). Variables analyzed included demographic characteristics, dysmenorrhea visual analog scale (VAS) scores, CA125 levels, baseline endocrine hormones, ovarian endometrioma characteristics, and uterine artery blood flow parameters including bilateral mean pulsatility index (PI), resistance index (RI), and systolic/diastolic ratio (S/D).

No significant differences were observed between groups regarding age (29.08 ± 4.64 vs. 30.42 ± 5.09, P = 0.078), body mass index (23.15 ± 2.37 vs. 23.54 ± 2.80, P = 0.333), parity, or baseline endocrine parameters. The miscarriage group showed significantly higher CA125 levels (33.53 ± 11.87 vs. 25.57 ± 10.54, P < 0.001), bilateral mean S/D ratio (7.90 ± 3.26 vs. 5.56 ± 2.06, P < 0.001), bilateral mean PI (2.51 ± 0.43 vs. 2.22 ± 0.45, P < 0.001), and VAS scores (median 3.00 vs. 1.00, P < 0.001). Multivariate logistic regression analysis revealed that bilateral mean S/D ratio (OR = 1.38, 95% CI: 1.15-1.66, P < 0.001) and CA125 levels (OR = 1.08, 95% CI: 1.04-1.12, P < 0.001) were independently associated with increased risk of early spontaneous miscarriage. ROC analysis demonstrated good predictive value for S/D ratio (AUC = 0.75, cutoff = 6.49) and CA125 (AUC = 0.76, cutoff = 23.55), with improved diagnostic accuracy when combined (AUC = 0.85, sensitivity = 0.87, specificity = 0.72).

Elevated serum CA125 levels and increased uterine artery S/D ratio are independently associated with increased risk of early spontaneous miscarriage in women with endometriosis with ovarian endometriomas smaller than 4 cm who conceive naturally. The combined assessment of CA125 levels and uterine artery S/D ratio during early pregnancy provides useful risk stratification for identifying high-risk patients, potentially enabling targeted interventions to improve pregnancy outcomes in these women.