A 29-year-old woman, gravida 1 para 0, at 35 weeks gestation comes to the emergency department due to possible leakage of amniotic fluid. The patient has had clear vaginal discharge for the past few hours. She has had no vaginal bleeding or contractions. Fetal movement is normal. The patient's pregnancy has been otherwise normal. She has no chronic medical conditions, and her only medication is a daily prenatal vitamin. Blood pressure is 128/76 mm Hg, and pulse is 84/min. The abdomen is soft and has no fundal tenderness. On sterile speculum examination, there is no pooling of fluid; nitrazine testing is negative. Microscopy reveals no ferning, clue cells, or motile organisms. A nonstress test is performed for 40 minutes, and results are shown in the exhibit. Ultrasound results are as follows:
Amniotic fluid volume Quadrant 1 3.7 cm Quadrant 2 4.3 cm Quadrant 3 2.1 cm Quadrant 4 4.4 cm Total 14.5 cm (normal >5 cm) Biophysical profile Breathing 2 Movement 2 Tone 2 Amniotic fluid volume 2
Which of the following is the best next step in management of this patient?
Antepartum fetal surveillance | |||
Test | Description | Normal result | Abnormal result |
Nonstress | External fetal heart rate monitoring for 20-40 minutes |
|
|
Biophysical profile |
| 8 or 10 points |
|
Contraction stress test | External fetal heart rate monitoring during spontaneous or induced (eg, oxytocin, nipple stimulation) uterine contractions | No late or | Late decelerations with >50% of contractions |
Doppler sonography of the umbilical artery | Evaluation of umbilical artery flow in fetal intrauterine growth restriction only | High-velocity diastolic flow in umbilical artery | Decreased, absent, or reversed end-diastolic flow |
This patient at 35 weeks gestation is evaluated for possible preterm prelabor rupture of membranes (PPROM). Patients with high-risk pregnancies or acute obstetric conditions (eg, suspected PPROM, vaginal bleeding, decreased fetal movement) require evaluation for fetal well-being with a nonstress test (NST), which is continuous fetal heart rate monitoring for 20-40 minutes. An NST result is normal (ie, reactive) if ≥2 fetal heart rate accelerations are present (with normal baseline, variability, and no decelerations), indicating that fetal oxygenation is adequate and the risk of fetal acidemia is low.
In contrast, this patient has a nonreactive NST result (ie, <2 accelerations), which can be due to a benign cause (eg, fetal sleep cycle) or indicate potential fetal hypoxia/acidemia. Because a nonreactive NST result is nonspecific, it requires further evaluation with a biophysical profile (BPP), an ultrasound test that assigns a score of 0 or 2 to each of the following 5 parameters: NST, fetal tone, movement, breathing, and amniotic fluid. An 8 of 10 score, as in this patient (ie, −2 for nonreactive NST), is normal. Patients with a nonreactive NST result and normal BPP score receive reassurance and routine care.
(Choice A) Patients at continued risk for acute fetal deterioration (eg, after maternal abdominal trauma, bleeding placenta previa) require 24-hour continuous monitoring. This patient is not at risk for acute fetal compromise, so continuous monitoring is not necessary.
(Choice B) A contraction stress test is used to assess fetal well-being if BPP results are equivocal (ie, score of 6 of 10).
(Choice C) Immediate delivery may be indicated for severe recurrent fetal heart rate decelerations, which typically indicate fetal hypoxia and acidemia. In contrast, a nonreactive NST result is followed by evaluation with a BPP. If the BPP result is also abnormal (eg, no fetal tone, no fetal movement), delivery may be indicated.
(Choice E) Umbilical artery Doppler ultrasonography is used to monitor fetal growth restriction (ie, estimated fetal weight <10th percentile). This patient's pregnancy has been uncomplicated.
Educational objective:
In the assessment of fetal well-being, a nonreactive nonstress test result (ie, <2 fetal heart rate accelerations in 20-40 minutes) is nonspecific for fetal hypoxia and acidemia and requires further evaluation with a biophysical profile (BPP). A normal BPP score is 8-10 of 10. Patients with a nonreactive nonstress test result and normal BPP score receive reassurance and routine care.