The primary goal of antenatal testing is to identify fetuses at risk of intrauterine neurologic injury or death so that these adverse outcomes can be prevented. Many techniques for assessment of fetal well-being have been introduced into clinical practice, beginning in the 1970s (table 1). Despite widespread use of these techniques, there is limited evidence to guide their optimal use or to demonstrate their effectiveness at improving perinatal outcomes.
This topic will provide an overview of fetal assessment. Detailed discussions of the various techniques used and conditions where antenatal assessment is indicated are available separately. (See individual topic reviews).
Fetal hypoxia and acidosis represent the final common pathway to fetal injury and death in many high risk pregnancies . The basis for antepartum testing is the premise that the fetus whose oxygenation in utero is challenged will respond with a series of detectable physiologic adaptive or decompensatory signs as hypoxemia or frank metabolic acidemia develop. For example:
●Blood flow is directed to the brain, heart, and adrenals and away from the kidney. The reduction in renal perfusion leads to decreased fetal urine production, which results in decreased amniotic fluid volume.
●Fetal movements decrease as the fetus attempts to conserve energy . The loss of fetal movement can be a sign of ongoing central nervous system hypoxia and injury.