Association Between Third-Trimester Ultrasonography With Histopathological Changes in the Placenta Among Mothers With Gestational Diabetes Mellitus

Background Gestational diabetes mellitus (GDM) is a prevalent metabolic disorder during pregnancy, associated with significant maternal and fetal complications. GDM affects placental structure and function, potentially compromising fetal development. Third-trimester ultrasonography (USG) serves as a non-invasive tool for fetal and placental assessment, while histopathological examination provides definitive evidence of placental changes. This study aimed to evaluate the correlation between third-trimester USG findings and placental histopathological changes in GDM pregnancies. Methodology A hospital-based observational study was conducted over 18 months at a tertiary care center in Chennai. A total of 85 pregnant women diagnosed with GDM after 28 weeks of gestation were included. All participants underwent third-trimester USG to assess placental thickness, estimated fetal weight (EFW), amniotic fluid index (AFI), and placental grading. After delivery, placentas were collected and examined histopathologically for changes such as syncytial knots, chorangiosis, fibrinoid necrosis, and intervillous thrombosis. Data were analyzed using SPSS (IBM SPSS Statistics for Windows, IBM Corp., Version 26, Armonk, NY), and associations between USG and histopathological findings were assessed using independent t-tests. Results A total of 85 women with gestational diabetes were studied. Nearly half were aged 26-30 years (42, 49.4%), while 20 (23.5%) were 31-35 years. Management was most commonly with oral hypoglycemic agents (40, 47.1%), followed by medical nutrition therapy (21, 24.7%). Antenatal steroids were administered in 38 (44.8%). Most USG examinations were at 31-32 weeks (40, 47.1%). Term deliveries (37-38 weeks) occurred in 77 (90.6%), with 52 (61.2%) vaginal and 33 (38.8%) caesarean births. Placental grading showed Grade 3 in 78 (91.7%). Histopathology frequently revealed syncytial knots, chorangiosis, fibrinoid necrosis, and intervillous thrombosis, significantly associated with increased placental thickness and EFW. Conclusion Third-trimester USG findings, particularly increased placental thickness and EFW, correlate significantly with histopathological changes in GDM placentas. These findings underscore the value of antenatal USG as a predictive tool for placental pathology and potential adverse outcomes in GDM pregnancies.