Fetal well-being: Nonimaging assessment and the biophysical profile

Abstract

All of the testing methods described above are very good at predicting continued fetal health when test results are reassuring. Each test also suffers from a very poor ability to predict compromise when results are abnormal. Thus, the primary value of antepartum fetal monitoring is in identifying those pregnancies that do not require immediate intervention and may be allowed to continue. Certainly, all pregnant women (regardless of risk status) should monitor fetal movement as part of their fetal surveillance. For patients at risk, a variety of testing schemes are available using combinations of the NST, CST and BPP. There are several reasons for using the NST as the primary testing method for those at risk. Even a small antenatal testing area can accommodate three or four FHR monitors, and a single antenatal testing nurse can perform several NSTs at a time. Because the BPP requires an ultrasound machine and a trained technician to perform, and because only one BPP can be done at a time, many obstetricians who do their own in-office fetal testing are unable to adopt BPP testing as their primary means of surveillance. Additionally, it is more economical to use the NST than the BPP for first-line testing. Assuming charges of $150 and $300 for the NST and BPP, respectively, and assuming that 20% of NSTs are nonreactive and require a BPP for second-line testing, the weekly cost of testing 100 patients is $21,000 for the NST and $37,500 for the BPP. This increase-in-testing cost must be balanced against the small improvement in perinatal mortality rates achieved with the use of the BPP. Because it must be performed in a hospital setting and takes an average of 90 minutes to complete, the CST is more expensive and time-consuming than either the NST or BPP and it is less frequently used as the primary method of fetal testing. In the past the CST was the most commonly used secondary test after a nonreactive NST, but use of the BPP in this situation has now become commonplace. Although the CST still has an important role in fetal testing, the BPP is better suited for use in this setting because of its technical ease and low incidence of abnormal results. Thus, many centers use the NST as the primary mode of testing for the fetus at risk, often with a sonographic assessment of AFV. Nonreactive NSTs require further assessment, and the BPP is often used for this purpose. Use of the BPP as the primary testing method is easiest in centers with the technical ability to perform a large number of ultrasound examinations. The CST is rarely used in most centers, but is important in identifying those fetuses likely to tolerate an induction of labor.