The first sign of hypovolemic shock from postpartum hemorrhage is likely to be:

Check the client's fundus. Lochia rubra is the normal vaginal bleeding and discharge that occurs after childbirth. It consists of blood, mucus, and tissue from the placenta and the uterus lining. It is usually bright red and may have some clots, but these clots should not be big or difficult to pass. If the client has a large amount of lochia rubra with several clots, it may indicate that the uterus is not contracting well and needs to be massaged to expel any retained tissue or blood. Checking the client's fundus is the first action the nurse should take to assess the uterine tone and location.

Choice A is incorrect because requesting the provider perform a vaginal examination is not the first action the nurse should take. A vaginal examination may be necessary if the fundal massage does not reduce the bleeding or if there is a suspicion of lacerations or hematoma, but it is not a priority intervention.

Choice C is incorrect because measuring the client's vital signs is not the first action the nurse should take. Vital signs can help monitor the client's hemodynamic status and identify signs of shock, such as tachycardia, hypotension, and pallor, but they are not as important as checking the fundus in this situation.

Choice D is incorrect because feeling for a full bladder is not the first action the nurse should take. A full bladder can displace the uterus and interfere with its contraction, leading to increased bleeding. However, it is not as likely as uterine atony to cause a large amount of lochia rubra with several clots.

Hemorrhage. This is because postpartum hemorrhage (PPH) is severe bleeding and loss of blood after childbirth that can lead to death. The most common cause of PPH is the uterus not contracting properly after delivery. The nurse needs to monitor the client’s pulse and blood pressure frequently to detect signs of shock and blood loss.

Choice A is wrong because thromboembolism is a blood clot that blocks a blood vessel, not a complication of bleeding.

Choice B is wrong because cervical laceration is a tear in the cervix that can cause bleeding, but it is not a common cause of PPH.

Choice C is wrong because hemorrhoids are swollen veins in the anus or rectum that can cause bleeding, but they are not a common cause of PPH.