en <p>Background: Low-dose aspirin (ASA) is used in obstetrics for different indications, mainly to prevent preeclampsia. This study investigated the underlying mechanism of ASA&rsquo;s effect on the fetus&rsquo;s cardiovascular functions.<br /> Methods: 42 pregnant women at 18-24 weeks of gestation, identified as high-risk for preeclampsia, received 160 <em>mg</em> of ASA daily. Fetal Doppler ultrasound was performed before and three weeks after ASA treatment, assessing ductus venosus, middle cerebral, umbilical, and uterine arteries pulsatility indices as well as pulmonary, aorta, and superior vena cava (SVC) diameters in the three-vessel view, including pulmonary/aorta and SVC/aorta ratios. All analyses were performed using SPSS software version 27, with a significance threshold set at p&lt;0.05. A paired t-test was used to assess differences in means. The Chi-square and Fisher&rsquo;s exact test analyzed nominal variables.<br /> Results: Post-intervention analysis revealed significant improvements in abnormal uterine artery resistance (p&lt;0.001) and abnormal pulsatility index of the umbilical artery, middle cerebral artery, and ductus venosus (p&lt;0.001 for all). Moreover, 160 <em>mg/day</em> aspirin administration significantly increased mitral E/A (early filling velocity/atrial contraction velocity: 0.397&plusmn;0.029; p&lt;0.001), diameters of aorta (4.390&plusmn;0.852; p&lt;0.001), pulmonary artery (4.895&plusmn;1.087; p&lt;0.001), and SVC (2.511&plusmn;0.535; p&lt;0.001), while significantly decreasing left ventricular myocardial performance index (p&lt;0.05).<br /> Conclusion: Daily administration of 160 <em>mg</em> of aspirin enhances fetal vascular and cardiac function. Evaluating fetal cardiovascular parameters beyond routine uterine artery Doppler, especially in high-risk pregnancies, and initiating ASA therapy in cases of insidious abnormalities, may help delay or prevent fetal complications such as intrauterine growth restriction (IUGR) by improving cardiovascular function.</p> Aspirin, Cardiovascular functions, Ultrasound imaging, Obstetrics 165 172 https://www.jri.ir/article/140279 https://www.jri.ir/documents/fullpaper/en/140279.pdf BehrokhSahebdelDepartment of Obstetrics and Gynecology, Yas Hospital complex, Tehran University of Medical Sciences, Tehran, Iran122840Mohammad NasirHematianDepartment of Perinatology and Fetal Cardiology, Yas Hospital complex, Tehran University of Medical Sciences, Tehran, Iran122918ZohrehHeidaryVali-E-Asr Reproductive Health Research Center, Family Health Research Institute, Tehran University of Medical Sciences, Tehran, Iran51898FatemehGolshahiDepartment of Obstetrics and Gynecology, Yas Hospital complex, Tehran University of Medical Sciences, Tehran, Iran122844NafisehSaediDepartment of Obstetrics and Gynecology, Yas Hospital complex, Tehran University of Medical Sciences, Tehran, Iran122845FatemehRahimi-SharbafDepartment of Obstetrics and Gynecology, Yas Hospital complex, Tehran University of Medical Sciences, Tehran, Iran122919MahboobehShiraziDepartment of Obstetrics and Gynecology, Yas Hospital complex, Tehran University of Medical Sciences, Tehran, Iran122847ArianTavasolStudent Research Committee, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran122920GitaManzari TavakoliPediatric Urology and Regenerative Medicine Research Center (PURMRC), Gene, Cell and Tissue Research Institute, Tehran University of Medical Sciences, Tehran, Iran122921Mohammad HosseinGolezarAdvanced Diagnostic and Interventional Radiology Research Center (ADIR), Tehran University of Medical Sciences, Tehran, Iran122922HamedGhoraniAdvanced Diagnostic and Interventional Radiology Research Center (ADIR), Tehran University of Medical Sciences, Tehran, Iran122923ElhamFeizabadDepartment of Obstetrics and Gynecology, Yas Hospital complex, Tehran University of Medical Sciences, Tehran, Iran122924SoudabehRezaeiDepartment of Obstetrics and Gynecology, Yas Hospital complex, Tehran University of Medical Sciences, Tehran, Iransodabe.rezaei80@gmail.com122925