Acetaminophen is a common over-the-counter medication taken for fever and pain relief, during pregnancy. However, concerns have emerged regarding its potential to induce constriction of the ductus arteriosus, which is an essential fetal vessel. This case series investigated the potential association between acetaminophen usage during pregnancy and fetal ductus arteriosus constriction. This study is based on four pregnant patients who took acetaminophen at different stages of pregnancy and experienced premature constriction of the ductus arteriosus, in the fetus. The cases were identified on fetal echocardiograms, and pertinent details such as maternal acetaminophen usage, gestational age, ductus arteriosus characteristics, and clinical outcomes were gathered from medical records. All cases demonstrated ductus arteriosus constriction, with improvement seen in ductal velocities in two of the cases, after acetaminophen cessation. The additional case had sustained elevated velocities, with a stable outcome. The final case had progression of ductal constriction, leading to right ventricular dilation, and cesarean delivery at 36 weeks. Maternal acetaminophen use varied across the three trimesters. This case series underscores a potential link between acetaminophen use, during pregnancy, and premature constriction of the ductus arteriosus. Further research is needed to examine the correlation between acetaminophen exposure and premature constriction of the ductus arteriosus.