Viable fetus

Fetal distress can be caused by a host of factors; most notably, hypoxemia and hypovolemia are dangerous for the viable fetus. It is not uncommon for a pregnant patient to be affected by critical illness.

Examples of nonobstetric maladies that lead to intensive care unit admission among pregnant women are hematologic issues (venous thromboembolism and pulmonary embolus, pre-pregnancy hypercoagulable states), trauma (including motor vehicle accidents, falls, assaults, burns, etc.), asthma, valvular and congenital heart disease, and acute abdominal conditions (appendicitis, ruptured viscus associated with peptic ulcer disease, and inflammatory bowel disease).

After approximately 24 weeks of gestation, most authorities consider the viable fetus to be alive, so for many pregnant patients in the intensive care unit (ICU) care must also be directed to the viable fetus.

Although maternal life should never be jeopardized for the care of this second patient, the critical care physician should be able to recognize signs of fetal distress and collaborate with obstetric and neonatology colleagues to determine optimal therapy for both patients.

Fetal tachycardia, late fetal heart rate decelerations, and loss of heart rate variability of a viable fetus are signs of significant fetal distress and call for immediate action. These are best identified with the use of the continuous electronic fetal monitor.

Although there is a lack of high-quality evidence, it is probably rational to use electronic fetal monitoring for any patients with estimated gestational age of 24 weeks or greater.

The electronic fetal monitor consists of two probes placed on the mother’s abdomen. One probe uses ultrasound (Doppler) to transmit and record the fetal heart rateof the viable fetus.

The second sensor is a pressure-sensitive device that records frequency and duration of uterine contractions. Fetal monitoring may demonstrate fetal distress, but changes in viable fetus heart rate are nonspecific and are often a late sign of inadequate fetal oxygen delivery.

It is most accurate when performed at 32 weeks of gestation or later. The most specific indicator of fetal distress is probably fetal pH monitoring, which is performed by scalp blood sampling.

However, to access the viable fetus scalp, cervical dilation must have begun and membranes must be ruptured, so this in not practical for many of the gravid patients in the ICU.

If fetal distress or premature labor occurs, the first call should be to the obstetric service. Their expertise in assessment of gestational age, electronic fetal monitoring, maintenance of uterine blood flow, medication use, and the decision to perform emergency cesarean section are invaluable to the mother and viable fetus.

Oxygen delivery to the viable fetus should be optimized by providing supplemental oxygen and restoring adequate circulating volume and cardiac function to the mother.

Prevention of compression of the inferior vena cava by the gravid uterus is accomplished with placement of the mother in the left lateral decubitus position.

If premature labor has commenced, tocolysis may be indicated to halt labor or delay delivery. Maternal steroid administration has been demonstrated to promote fetal lung maturity. However, delivery of the viable fetus may be the best option for the mother and the fetus.

Suggested Readings

Viable fetus Hall JB, Schmidt GA, Wood LDH, eds. Principles of Critical Care, 3rd ed. New York: McGraw-Hill

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