Editing Maternal and Newborn Nursing (section)

=== Cardiovascular and hematologic ===

* Blood volume rises roughly 40 to 50 percent; plasma volume rises proportionally more than red cell mass, producing '''physiologic (dilutional) anemia of pregnancy'''. Hemoglobin below about 11 g/dL in the first and third trimesters, or below about 10.5 g/dL in the second, suggests true anemia.
* Cardiac output rises about 30 to 50 percent, mostly from increased stroke volume early and heart rate later. Resting pulse increases roughly 10 to 15 beats per minute.
* Blood pressure ''falls'' in the first and second trimesters because systemic vascular resistance drops, reaching a nadir near mid-pregnancy, then returns toward the prepregnancy baseline near term. A blood pressure that ''rises'' after 20 weeks is never dismissed as normal pregnancy change.
* Pregnancy is a '''hypercoagulable state''' (increased fibrinogen and clotting factors, decreased fibrinolysis). This limits hemorrhage at delivery but raises venous thromboembolism risk throughout pregnancy and especially postpartum.
* '''Supine hypotensive syndrome (aortocaval compression)''': after about 20 weeks the gravid uterus compresses the inferior vena cava when the patient lies flat, dropping venous return, cardiac output, and uteroplacental perfusion. Signs are dizziness, pallor, nausea, hypotension, and a nonreassuring fetal heart rate. '''Intervention: turn the patient to a lateral position, classically left lateral.''' This is the single most common test answer for maternal hypotension or a sudden fetal heart rate change in a supine patient.