Which of the following findings would cause concern when a client's water has broken and labor has started?

When a client’s water has broken and labor has commenced, the presence of green fluid on a peri-pad is concerning due to the potential implications for fetal well-being. Green fluid typically indicates the presence of meconium. Meconium-stained amniotic fluid suggests that the fetus may be experiencing distress, leading to a risk of meconium aspiration syndrome, where the newborn inhales a mixture of meconium and amniotic fluid into the lungs, which can cause respiratory issues after birth.

Other findings such as normal maternal vital signs, blood and mucus on the perineal pad, and a baseline fetal heart rate within a normal range do not pose immediate concerns. Normal maternal vital signs indicate that the mother is stable. The presence of blood and mucus can be common during labor, particularly as cervical changes occur, and does not necessarily indicate distress. Similarly, a fetal heart rate within a normal range suggests that the fetus is not in distress at that moment. Therefore, the presence of green fluid is a significant finding that warrants further evaluation and monitoring, making it the correct answer in this context.