# Clinical characteristics and associated risk factors for diminished ovarian reserve among Chinese women: a matched case-control study

## TL;DR

This study identifies risk factors for diminished ovarian reserve in Chinese women, including infections and lifestyle factors, with age-related differences in their impact.

## Contribution

The study provides novel insights into TORCH infections and demographic factors as risk indicators for DOR in a Chinese population.

## Key findings

- Non-Han ethnicity, obesity, and T. gondii infection were independently associated with DOR.
- TORCH infections showed strong associations with DOR in younger women (20–35 years) but not in older women (36–47 years).
- Age-related effect modification was observed for pregnancy history and infections.

## Abstract

Diminished ovarian reserve (DOR) has emerged as a significant reproductive challenge and a broader societal concern. Most previous studies have focused on ovarian reserve markers, while limited research has examined DOR as a primary outcome, and the potential association between TORCH infections (toxoplasmosis, others, rubella, cytomegalovirus, herpes) and DOR risk remains unclear.

A matched case–control study was conducted among women aged 20–47 years who sought assisted reproductive technology at a maternity hospital in Sichuan, China, between January 2022 and August 2024. DOR was diagnosed according to the Consensus on clinical diagnosis and management of diminished ovarian reserve from China. Age-matched controls (1:1) with normal ovarian reserve were selected. Conditional logistic regression was used to identify factors associated with DOR, with multivariable models adjusting for confounders. Subgroup analyses by age and body mass index (BMI) were conducted to examine robustness and effect modification.

A total of 3,751 DOR cases were matched to 3,751 controls (median age: 36 years). DOR group had significantly higher FSH, E2, and LH levels (P < 0.01), and lower AFC, AMH, PRL, and T levels (P < 0.001) compared to controls. Multivariable logistic regression showed that non-Han ethnicity (OR = 1.278, 95% CI: 1.115–1.466), manual labor (OR = 1.181, 95% CI: 1.002–1.392), obesity (OR = 1.316, 95% CI: 1.044–1.660), light menstrual flow (OR = 1.262, 95% CI: 1.111–1.435), and T. gondii infection (OR = 2.292, 95% CI: 1.683–3.122) were independently associated with DOR. In women aged 20–35 years, ≥2 pregnancies (OR = 0.712, 95% CI: 0.615–0.824), and infections with T. gondii (OR = 23.750, 95% CI: 13.330-42.316), CMV (OR = 8.189, 95% CI: 5.821-11.521), and RV (OR = 8.132, 95% CI: 5.806-11.390) were strongly associated with DOR, with no such associations observed in the 36–47 years group. Significant age interactions were detected (P < 0.05).

Ethnicity, obesity, menstrual flow, pregnancy history, and TORCH infections were significantly associated with DOR, with age-related effect modification observed for pregnancy history and infections. Prospective studies are needed to elucidate the underlying mechanisms, particularly the role of infections and immune response.