Impact of 50 g OGTT-Induced Acute Hyperglycemia on Uteroplacental and Fetoplacental Circulations in Gestational Diabetes Screening: A Prospective Single-Center Study

<b>Background:</b> Gestational diabetes screening often employs the 50 g oral glucose tolerance test (OGTT), which induces acute hyperglycemia. This study aimed to investigate the effects of this acute hyperglycemia on uteroplacental and fetoplacental circulations in women between the 24th and 28th weeks of pregnancy using Doppler ultrasonography (USG). <b>Methods:</b> This prospective, single-center study included 209 pregnant women with singleton pregnancies followed at Bursa City Hospital between January and April 2021. Doppler USG measurements were taken before and 60 min after administering the 50 g OGTT. Venous blood samples were collected to measure blood glucose levels pre-test and one hour post-test. Doppler indices, including the pulsatility index (PI), resistive index (RI), and systolic/diastolic ratio (S/D) for the uterine arteries, umbilical artery (UA), and middle cerebral artery (MCA), were recorded and converted to Z scores based on gestational age. Fetal biometric parameters, including abdominal circumference (AC), femur length (FL), and biparietal diameter (BPD), were also measured. <b>Results:</b> The study found a significant decrease in the mean MCA-PI, MCA RI, MCA S/D, and cerebroplacental ratio (CPR) values, as well as their respective Z scores, in the post-test measurements compared to pre-test values (<i>p</i> < 0.001 for all). No significant differences were observed in the S/D, RI, PI values, or Z scores of the uterine arteries and UA between pre-test and post-test measurements. <b>Conclusions:</b> Acute hyperglycemia induced by the 50 g OGTT significantly affects fetal cerebral circulation, evidenced by decreased MCA-PI, MCA RI, MCA S/D, and CPR values, but does not significantly impact uteroplacental circulation. Further large-scale studies are necessary to explore the effects of varying maternal glucose levels and the chronic impacts of non-physiological glucose levels on placental circulation.