A 23-year-old primigravid woman comes to the labor and delivery department due to decreased fetal movement for the past few days. She also has some regular, nonpainful uterine contractions but no vaginal bleeding or leakage of fluid. The patient has had no prenatal care but is estimated to be at 38 weeks gestation by her last menstrual period. She has no known medical conditions but has had fatigue and joint stiffness for the past month. Temperature is 99.1 F (37.2 C), blood pressure is 128/86 mm Hg, and pulse is 94/min. Fundal height is 37 cm. Physical examination shows an erythematous, confluent facial rash. The neck is supple. Cardiopulmonary examination is normal. The uterus is nontender. Fetal heart rate tracing is shown in the following exhibit. Which of the following is the most likely cause of this patient's fetal heart rate tracing?
This patient with fatigue, joint pain, and a malar facial rash most likely has systemic lupus erythematosus (SLE). SLE, like other autoimmune diseases, may improve, worsen, or initially present during pregnancy. Patients with SLE have an increased risk of obstetric complications, which can be maternal (eg, preeclampsia) or fetal (eg, neonatal lupus, intrauterine fetal demise).
Neonatal lupus occurs due to passive placental transfer of maternal anti-SSA (Ro) and anti-SSB (La) antibodies (which commonly occur in Sjogren but are also seen in ~30% of patients with SLE). Fetal findings are primarily cardiac and cutaneous (eg, scalp or periorbital rash). The most serious complication is fetal atrioventricular (AV) block, which develops at 18 to 24 weeks gestation. This likely occurs due to maternal autoantibodies binding to fetal cardiac cells and causing irreversible injury to the AV node. Without normal AV conduction, the ventricular heart rate (eg, 50-80/min) determines the baseline fetal heart rate. On fetal heart rate tracing, this appears as persistent fetal bradycardia (ie, <110/min).
With prolonged complete heart block, cardiomyopathy and hydrops fetalis may develop. Therefore, this patient with decreased fetal movement requires additional testing (eg, biophysical profile, fetal growth ultrasound) and possible delivery.
(Choice A) Congenital hypothyroidism can present with lethargy and bradycardia days to weeks after delivery; however, fetuses in utero are typically unaffected because some maternal thyroid hormone crosses the placenta.
(Choice C) A fetal sleep cycle can present with minimal or absent variability and decreased frequency of accelerations; however, the baseline fetal heart rate remains normal (eg, 110-160/min).
(Choice D) Incorrect gestational age dating can affect interpretation of the fetal heart rate tracing because fetuses at <32 weeks gestation have lower-amplitude accelerations and less variability. However, a baseline fetal heart rate of <110/min is abnormal at all gestational ages.
(Choice E) Intraamniotic infection may cause changes in the fetal heart rate tracing; however, it typically causes fetal tachycardia (not bradycardia). In addition, there is usually fever and uterine tenderness, which are not seen in this patient.
Educational objective:
Patients with systemic lupus erythematosus have an increased risk of obstetric complications. Neonatal lupus can occur due to passive placental transfer of maternal anti-SSA (Ro) and anti-SSB (La) antibodies. Patients may develop fetal atrioventricular block, which appears on fetal heart rate tracing as persistent bradycardia.