Abstract
Background: Hydronephrosis is a common physiological condition during pregnancy caused by hormonal and mechanical changes that lead to dilatation of the urinary tract. However, maternal obesity may further increase the severity and occurrence of hydronephrosis due to increased intra-abdominal pressure, altered renal hemodynamics, and impaired urinary drainage. Ultrasonography remains the preferred imaging modality for evaluating hydronephrosis in pregnancy because it is safe, non-invasive, and free from ionizing radiation.
Objectives: This study aimed to evaluate the relationship between maternal body mass index (BMI) and the ultrasonographic grading and incidence of hydronephrosis in pregnant women receiving antenatal care.
Methodology: A cross-sectional analytical study was conducted in the Obstetrics and Gynecology Department in collaboration with the Radiology Department of a tertiary care hospital. A total of 60 pregnant women in the second and third trimesters were recruited using a non-probability convenience sampling technique from October 2025 to April 2026. Demographic, obstetric, clinical, and ultrasonographic data were collected through a structured questionnaire. Height and weight were measured using standard hospital instruments, and BMI was calculated using the standard formula: BMI = weight (kg)/height (m²). Participants were classified according to WHO BMI categories. Renal ultrasonography was performed by certified radiologists to assess the presence, side involvement, and grading of hydronephrosis as mild, moderate, or severe. Statistical analysis was performed to determine the association between maternal BMI and hydronephrosis.
Results: The findings demonstrated a significant relationship between maternal BMI and the occurrence and ultrasonographic grading of hydronephrosis in pregnant women. Women with elevated BMI showed a greater frequency of moderate to severe hydronephrosis compared to women with normal BMI. Right-sided hydronephrosis was observed more frequently, which is consistent with the normal anatomical and physiological changes during pregnancy. Ultrasonography proved to be a reliable and effective diagnostic method for evaluating hydronephrosis and distinguishing physiological dilatation from clinically significant renal involvement. Maternal obesity was associated with increased intra-abdominal pressure, vascular congestion, altered renal blood flow, and impaired urinary drainage, contributing to increased severity of hydronephrosis.
Conclusion: Maternal BMI is significantly associated with the incidence and ultrasonographic grading of hydronephrosis during pregnancy. Pregnant women who are overweight or obese may require closer antenatal monitoring to prevent complications such as urinary tract infections, flank pain, renal impairment, and the need for invasive interventions. Since BMI is a modifiable risk factor, early identification and appropriate prenatal management may improve maternal renal health and pregnancy outcomes. Routine BMI assessment should therefore be considered an important component of antenatal evaluation for hydronephrosis. Further multicenter studies with larger sample sizes are recommended to strengthen the evidence and support the development of BMI-based screening and management protocols for maternal hydronephrosis.