Introduction
Obstetric care providers have two patients: the mother and the fetus. Assessment of maternal wellbeing is relatively easy, but fetal wellbeing is far more difficult to assess. Several tests have been developed to confirm fetal wellbeing before labor and delivery (Figure 52.1).
Goal
- There are many causes of irreversible neonatal cerebral injury, including congenital abnormalities, intracerebral hemorrhage, hypoxia, infection, drugs, trauma, hypotension, and metabolic derangements (hypoglycemia, thyroid dysfunction).
- Antenatal fetal testing cannot predict or reliably detect all of these causes. The goal of antepartum fetal surveillance (Figure 52.2) is early identification of a fetus at risk for preventable morbidity or mortality due specifically to uteroplacental insufficiency.
- Antenatal fetal tests make the following assumptions:
1 that pregnancies may be complicated by progressive fetal asphyxia which can lead to fetal death or permanent handicap
2 that current antenatal tests can adequately discriminate between asphyxiated and non-asphyxiated fetuses
3 that detection of asphyxia at an early stage can lead to an intervention, which is capable of reducing the likelihood of an adverse perinatal outcome.
It is not clear whether any of these assumptions are true. At most, 15% of cerebral palsy is due to birth asphyxia.
Note. All antepartum fetal tests should be interpreted in light of the gestational age, the presence or absence of congenital anomalies, and underlying clinical risk factors.
Antepartum fetal tests
Non-stress test (NST)
- Also known as cardiotocography (CTG).
- NST refers to changes in the fetal heart rate pattern with time (see Chapter 65). It reflects maturity of the fetal autonomic nervous system. NST is non-invasive, simple to perform, readily available, and inexpensive. However, interpretation is largely subjective.
- Is a “reactive” NST (R-NST) reassuring?
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