Gestational diabetes mellitus (GDM) is associated with significant maternal and fetal complications. The standard diagnostic test for GDM is the 75-gram oral glucose tolerance test (OGTT). However, pregnant women who have undergone bariatric surgery may not tolerate OGTT due to dumping syndrome and gastrointestinal side effects. This creates diagnostic challenges in this specific population.

The aim of this prospective observational study is to evaluate whether routinely measured glycemic markers, including fasting blood glucose, postprandial blood glucose, HbA1c, and urinary glucose levels, can predict the development of gestational diabetes mellitus and related pregnancy complications in women with prior bariatric surgery.

Pregnant women aged 18-50 years with a history of bariatric surgery will be enrolled and followed throughout pregnancy. The predictive value of glycemic markers for GDM, macrosomia, and polyhydramnios will be analyzed using multivariable logistic regression models.

This study aims to provide alternative diagnostic approaches for GDM screening in pregnant women who are unable to tolerate OGTT and to contribute to improving maternal and perinatal outcomes in this growing patient population.

Gestational diabetes mellitus (GDM) is a common pregnancy complication associated with increased risks of maternal and perinatal morbidity. Early identification and appropriate management are essential to reduce adverse outcomes such as macrosomia, polyhydramnios, and cesarean delivery.

The standard diagnostic approach for GDM is the 75-gram oral glucose tolerance test (OGTT). However, women with prior bariatric surgery frequently experience intolerance to glucose loading due to dumping syndrome, which limits the reliability and feasibility of OGTT in this population. Consequently, alternative diagnostic strategies are required.

This prospective observational cohort study will be conducted at Prof. Dr. Cemil Taşcıoğlu City Hospital between February 2026 and December 2027. Pregnant women aged 18-50 years with a history of bariatric surgery will be enrolled during the first or second trimester. Participants will be categorized according to OGTT tolerance (tolerated vs. not tolerated/refused).

Baseline demographic characteristics including maternal age, gravidity, parity, obstetric history, and educational status will be recorded. Glycemic parameters assessed during routine antenatal follow-up will include fasting plasma glucose, postprandial glucose, HbA1c levels, and urinary glucose measurements. Second and third trimester ultrasound findings will be documented. Pregnancy outcomes including diagnosis of GDM, macrosomia (birth weight >4000 g), and polyhydramnios will be recorded.

The primary objective is to evaluate the predictive value of routine glycemic markers for GDM. Secondary objectives include assessing their association with macrosomia and polyhydramnios.

Statistical analyses will be performed using SPSS version 27. Continuous variables will be summarized as mean ± standard deviation or median (interquartile range) depending on distribution. Comparisons between groups will be performed using the Mann-Whitney U test. Multivariable logistic regression models will be used to determine independent predictors of GDM and other pregnancy complications after adjustment for potential confounders.

This study aims to provide evidence for alternative screening approaches in pregnant women with prior bariatric surgery who are unable to tolerate OGTT and to improve clinical decision-making in this growing patient population.

Inclusion Criteria

• Pregnant women aged 18-50 years
• Singleton pregnancy
• History of bariatric surgery prior to pregnancy
• Followed at Prof. Dr. Cemil Taşcıoğlu City Hospital, Department of Obstetrics and Gynecology
• Availability of glycemic parameters during early pregnancy (≤14 weeks) and/or between 24 and 28 weeks of gestation (fasting plasma glucose, HbA1c, urine glucose, and/or OGTT results if tolerated)
• Availability of sonographic and clinical follow-up data between 28 weeks of gestation and delivery (up to 40 weeks) Exclusion Criteria
• Age <18 years or >50 years
• Multiple pregnancy
• Presence of known chronic systemic disease (e.g., pregestational diabetes or endocrine disorders)
• Incomplete or missing clinical data

The study population consists of pregnant women aged 18-50 years with a history of bariatric surgery prior to conception who were followed at the Department of Obstetrics and Gynecology of Prof. Dr. Cemil Taşcıoğlu City Hospital. Eligible participants have documented glycemic parameters during the first and/or second trimester (including fasting plasma glucose, HbA1c, urine glucose and/or oral glucose tolerance test results) and available third trimester and/or delivery records. Only singleton pregnancies with complete clinical data are included.

Individual participant data (IPD) will not be shared due to institutional policies and national data protection regulations. Although this is a prospective study, the informed consent obtained from participants does not include permission for public data sharing. All collected data will be analyzed in de-identified form and handled in accordance with ethical approval and applicable data protection laws.