A 31-year-old woman, gravida 3 para 2, at 28 weeks gestation comes to the office for a prenatal visit. She has chronic hypertension that has been well controlled during this pregnancy. At the patient's previous prenatal visits, her blood pressure ranged from 120/70 to 130/80 mm Hg. Today, her blood pressure is 150/100 mm Hg and repeat is 152/98 mm Hg. Fundal height is 24 cm. Urinalysis shows 2+ protein. A transabdominal ultrasound reveals oligohydramnios and a fetus with growth restriction. Compared to normal placental parameters, this patient most likely has which of the following hemodynamic changes?

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11ec160b_3a00_e082_9249_458398959433_MD0001_00 This pregnant patient at ≥20 weeks gestation with hypertension (defined during pregnancy as systolic ≥140 mm Hg or diastolic ≥90 mm Hg) and proteinuria has preeclampsia. Risk factors include chronic hypertension or maternal vascular diseases (eg, diabetes mellitus, systemic lupus erythematosus). Preeclampsia is thought to occur due to abnormal development of placental cytotrophoblasts and the spiral arteries, which provide blood supply to the fetus and placenta. In healthy pregnancies, cytotrophoblasts act on the endothelial and muscular layers of the spiral arteries, changing the spiral arteries from small, tortuous vessels to high capacitance, low resistance vessels. These changes allow for increased uteroplacental perfusion and preferential supply of blood to the fetus for growth and development. However, in patients with preeclampsia, spiral arteries remain narrow and tortuous, resulting in high placental vascular resistance. This subsequently leads to decreased uteroplacental perfusion. As a result, the placenta cannot deliver adequate volumes of oxygenated blood to the fetus (ie, decreased umbilical vein oxygen delivery). The fetal response to inadequate oxygenation is to slow its growth (ie, fetal growth restriction) and preferentially shunt blood from the periphery (eg, kidneys) to the brain, leading to decreased fetal urine output and oligohydramnios, as seen in this patient. Educational objective: Patients with preeclampsia are at risk for fetal growth restriction and oligohydramnios due to abnormal placental spiral artery development, which leads to increased placental vascular resistance, decreased uteroplacental perfusion, and decreased umbilical vein oxygen delivery. __________ References: Mechanisms of endothelial dysfunction in hypertensive pregnancy and preeclampsia. (http://www.ncbi.nlm.nih.gov/pubmed/27451103)

A 31-Year-Old Woman, Gravida 3 Para 2, at 28 Weeks