Fluid Checks

Our care team conducts a fluid check with every NST. What would the care protocol look like if we start shifting some or all patient NSTs to a remote setting?

The most commonly used antenatal testing strategies include an NST alone, a modified biophysical profile (mBPP=an NST with an amniotic fluid check) or a full biophysical profile (BPP). ?As pointed out in the ACOG Practice Bulletin, each test is associated with a high negative predictive value, which is reported in the bulletin as 99.8% for an NST alone compared to 99.9% for a mBPP or complete BPP. Thus, each of these is commonly used as the primary modality a fetal testing program.

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The decision to add an AFI measurement to a fetal testing regimen is a clinical decision to be made by the clinical provider in balancing patient risk, the burden of in-person visits, and the potential impact and yield on clinical management.

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The ACOG Practice Bulletin quotes a false-negative rate (corrected stillbirth rate within 1 week of a negative test) of 0.8 per 1000 for a mBPP or full BPP compared to 1.9 per 1000 for an NST. However, it should be noted that 4 of the 13 “false negatives” in the reference paper (Miller et al., 1996) that suffered a stillbirth within a week after testing actually had a non-reactive NST, but were falsely reassured by an AFI>5cm and BPP 8/10.2 Moreover, when looking at other adverse outcomes, such as intrapartum compromise, an isolated non-reactive NST has a lower false-positive rate (43%) than an AFI<5cm (63%). ?The authors did not report the incidence of oligohydramnios in the setting of a non-reactive NST.

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Taking this into consideration, some of our Provider-Partners have restructured their care protocols to reduce the number of AFI measurements while maintaining frequent NSTs.

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Please note Nuvo does not dispense medical advice and can offer no independent guidance on how to structure an antenatal surveillance plan.?When a clinician is establishing a care plan, some points that may be considered, among others, include:

-??????Whether the patient is already scheduled to have one or more growth scans in the 3rd trimester, which provides an AFI measurement without increasing the patient or practice burden.?

-??????If they have other indications for in-office visits (e.g. in-person umbilical artery Doppler assessments for suspected fetal growth restriction).

-??????The individual threshold for recommending delivery. For example, if there is high concern for impending adverse outcome, or if they are post-dates when the incidence of oligohydramnios is elevated and the threshold for recommending delivery is low.

For some Provider-Partner sites, on top of clinical justifications for reducing the frequency of AFI measurements, there is also a social determinants of health justification. Many patients struggle to take off work, find childcare, and pay for transportation to physically come in for a BPP appointment. These providers would rather ensure patients have improved access to frequent NSTs through remote monitoring than infrequent in-clinic appointments that include AFIs.

Disclaimer: Nuvo does not provide medical advice, diagnosis or treatment.?The information above is intended solely as general educational material and is not intended to be used for any diagnostic purposes, and is not a substitute for professional medical advice.