A 29-year-old woman, gravida 1 para 0, at 34 weeks gestation comes to the office for a routine prenatal visit. She has had no contractions, vaginal bleeding, or leakage of fluid. Fetal movement is normal. The patient has systemic lupus erythematosus with positive anti-Ro/SSA antibodies but has had no flares during this pregnancy. Her medications include hydroxychloroquine, low-dose aspirin, and a prenatal vitamin. Blood pressure is 130/88 mm Hg and pulse is 65/min. Fundal height is 33 cm. The remainder of the physical examination is unremarkable. Urine dipstick has trace protein. A nonstress test is performed for 10 minutes; results are shown in the exhibit. Which of the following is the most likely etiology for this patient's fetal heart rate tracing?

Question

A 29-year-old woman, gravida 1 para 0, at 34 weeks gestation comes to the office for a routine prenatal visit.  She has had no contractions, vaginal bleeding, or leakage of fluid.  Fetal movement is normal.  The patient has systemic lupus erythematosus with positive anti-Ro/SSA antibodies but has had no flares during this pregnancy.  Her medications include hydroxychloroquine, low-dose aspirin, and a prenatal vitamin.  Blood pressure is 130/88 mm Hg and pulse is 65/min.  Fundal height is 33 cm.  The remainder of the physical examination is unremarkable.  Urine dipstick has trace protein.  A nonstress test is performed for 10 minutes; results are shown in the exhibit.  Which of the following is the most likely etiology for this patient's fetal heart rate tracing?

Quizplus · Accepted Answer

11ec25c8_da1c_a5d2_bc81_3dd811aa51cf_MD0003_00 The nonstress test (NST) is commonly performed for pregnancies at risk for fetal hypoxemia, acidemia, and/or demise due to a maternal or fetal comorbidity (eg, systemic lupus erythematosus, fetal growth restriction) or for decreased fetal movement. During an NST, the heart rate of a well-oxygenated fetus rises with fetal movement (accelerations). A reactive NST (eg, normal baseline, moderate variability, ?2 accelerations) has a high negative predictive value for fetal acidemia. This patient's NST is nonreactive because it has no accelerations. Nonreactive NSTs are concerning for fetal hypoxemia and acidemia; however, the most common cause of a nonreactive NST is a quiet fetal sleep cycle (which lasts ?40 min). patient's NST A typical NST is 20 minutes, but a nonreactive NST is extended (eg, 40-120 min) to ensure that fetal activity outside of quiet sleep is captured. Due to a high false-positive rate, nonreactive NSTs are further evaluated with either a biophysical profile or contraction stress test before concluding that the fetus may be hypoxemic and needs intervention. (Choice A) Congenital fetal heart block is a complication of systemic lupus erythematosus or Sjogren syndrome in pregnancy, due to anti-Ro/SSA antibodies crossing the placenta. However, fetal heart block typically causes fetal bradycardia (<110/min), not seen in this patient. (Choice B) Fetal head compression causes early decelerations, shallow decreases in the fetal heart rate that occur with contractions. These benign decelerations are likely the result of a fetal autonomic response to the alterations in intracranial pressure caused by contractions. There are no decelerations or contractions on this patient's NST. early decelerations (Choice C) Fetal heart rate accelerations require a mature sympathetic nervous system, which develops at 26-28 weeks gestation; therefore, extremely premature fetuses (<28 weeks gestation) often do not demonstrate reactivity. This patient is at 34 weeks gestation. (Choice E) Uteroplacental insufficiency causes late decelerations, which are shallow drops in the fetal heart rate of uniform depth and duration occurring after the onset of a contraction. late decelerations Educational objective: Quiet fetal sleep is the most common cause of a nonreactive nonstress test (eg, no accelerations). Because a fetal sleep cycle can last as long as 40 minutes, a nonreactive nonstress test is extended (eg, 40-120 min) to ensure that fetal activity outside of sleep is captured. References: What we have learned about intrapartum fetal monitoring trials in the MFMU Network. (http://www.ncbi.nlm.nih.gov/pubmed/27140936) Factors that increase reactivity during fetal nonstress testing. (http://www.ncbi.nlm.nih.gov/pubmed/24614020) The limits of electronic fetal heart rate monitoring in the prevention of neonatal metabolic acidemia. (http://www.ncbi.nlm.nih.gov/pubmed/27751795) Heart rate features in fetal behavioural states. (http://www.ncbi.nlm.nih.gov/pubmed/18757143)

A 29-Year-Old Woman, Gravida 1 Para 0, at 34 Weeks