Clinical meaning
Pregnancy involves profound physiological adaptations across virtually every organ system, all orchestrated to support fetal growth and development over approximately 40 weeks of gestation. Understanding these normal adaptations is essential for the practical nurse to differentiate expected changes from pathological findings during prenatal assessments. The cardiovascular system undergoes dramatic changes: blood volume increases by 40-50% (approximately 1.5 liters) to perfuse the growing uteroplacental unit, cardiac output increases by 30-50%, heart rate increases by 10-20 beats per minute, and peripheral vascular resistance decreases due to progesterone-mediated smooth muscle relaxation and increased nitric oxide production. These changes explain the physiological anemia of pregnancy (hemodilution), the sensation of palpitations, and the slight decrease in blood pressure during the second trimester. The respiratory system adapts through progesterone-stimulated increases in tidal volume (30-40% increase) and minute ventilation, creating a mild respiratory alkalosis (PaCO2 approximately 30 mmHg) that facilitates CO2 transfer from the fetal to the maternal circulation. The growing uterus elevates the diaphragm by approximately 4 cm, reducing functional residual capacity. The renal system experiences a 50% increase in glomerular filtration rate (GFR), which lowers serum creatinine and BUN levels. The ureters dilate (more prominent on the right due to dextrorotation of the uterus), increasing the risk of urinary tract infections and pyelonephritis. The endocrine system is central to pregnancy maintenance: human chorionic gonadotropin (hCG) from the trophoblast maintains the corpus luteum during early pregnancy, progesterone maintains the endometrium and suppresses uterine contractions, and human placental lactogen (hPL) promotes maternal insulin resistance to ensure glucose availability for the fetus. Prenatal care follows a structured schedule: monthly visits until 28 weeks, biweekly visits from 28-36 weeks, and weekly visits from 36 weeks until delivery. Leopold maneuvers are external palpation techniques used to determine fetal lie, presentation, position, and engagement. Fundal height measurement (in centimeters from the symphysis pubis to the uterine fundus) should approximate the gestational age in weeks between 20-36 weeks. The practical nurse assists with routine prenatal assessments, reinforces patient education on warning signs, administers prescribed prenatal supplements, and reports deviations from expected findings to the registered nurse or physician.