This exploratory study investigates the impact of fertility treatments on symptoms of irritable bowel syndrome (IBS) in women. Specifically, the study focuses on two groups:

• Women with polycystic ovary syndrome (PCOS) who are starting their first IVF cycle.
• Women who choose social freezing (freezing eggs for social reasons).

Background and Rationale PCOS is an endocrine disorder with hormonal and metabolic abnormalities associated with reduced fertility. There are four PCOS phenotypes, of which phenotypes A and B are the "classic" forms. Social freezing is becoming increasingly popular as an option for women without a partner who want to preserve their fertility.

IBS is a common gastrointestinal disorder involving motility disorders and a disturbed gut-brain axis. There is an increased risk of anxiety and depression in IBS patients. Women with PCOS have a twofold increased risk of developing IBS. However, little is known about the effect of hormonal fertility treatments on IBS symptoms.

Objectives

• Primary objective: To investigate whether fertility treatments influence the prevalence and severity of IBS symptoms.
• Secondary objective: To investigate this change in IBS prevalence and severity in relation to:
• Changes in anxiety and depression scores.
• Changes in general gastrointestinal complaints.
• Subgroup analyses based on:
• Type of stimulation
• Duration of desire to have children
• Ethnicity
• PCOS type
• Hormonal and ultrasound response

Study design The study is a prospective, interventional exploratory study in which participants complete questionnaires before and after the hormonal stimulation phase.

• Start date : March 1, 2026
• End date of data collection: February 2027
• Participation locations: Fertility Clinic UZ Brussels
• Target sample size: 120 women (60 per group)

Data collected

Before treatment:

• Demographics (height, weight, ethnicity)
• Medical history related to fertility
• PCOS phenotype (in study arm)

After treatment:

• Hormonal values (FSH, LH, estrogen, progesterone)
• Number of follicles on ultrasound
• Number of eggs collected

Questionnaires:

• IBS-SSS (IBS symptom severity)
• Rome IV and III criteria (IBS diagnosis)
• GSRS (general GI symptoms)
• PHQ-9 (depression)
• GAD-7 (anxiety)

Measuring instruments

• Rome IV and III criteria: Diagnosis of IBS based on frequency and nature of abdominal pain and changes in bowel movements.
• IBS-SSS: Five dimensions of IBS symptoms, score between 0 and 500.
• GSRS: General gastrointestinal complaints in five domains.
• PHQ-9 and GAD-7: Validation instruments for depression and anxiety.

Data management

• Data is collected manually using paper questionnaires.
• Data is then entered into RedCap.
• Analysis is performed using SPSS.
• Strict compliance with GDPR and confidentiality guidelines.

Statistical Analysis

• Logistic regression: To determine the likelihood of meeting the Rome criteria before and after treatment.
• Multiple linear regression: To identify factors that influence change in IBS-SSS scores.
• Model selection: Based on AIC (Akaike Information Criterion).
• Separate analyses for PCOS and social freezing groups.

Inclusion Criteria:

• Diagnosis of PCOS according to the 2004 Rotterdam criteria (only for the PCOS group and not for the social freezing group)
• Initiating their first cycle of IVF treatment (PPOS and freeze only protocol)
• Nulliparous
• ≥ 18 years
• Willing to participate in the study
• Understanding Dutch, French or English

Exclusion Criteria:

• - Known inflammatory bowel disorder
• Known major intestinal bowel disorder
• Known systemic or auto-immune disorder with implication for the GI system
• History of abdominal surgery (appendectomy and cholecystectomy allowed if >6 months earlier)
• History of gastro-enteritis in the past 6 weeks