Ob-Gyn Coding Alert

Antepartum fetal stress testing can be a difficult area for many ob/gyn coders. Choosing the correct diagnosis code and matching CPT code often necessitates an in-depth understanding of the indications for these tests. In addition, some of these tests are not a routine part of antepartum care and, as such, require additional documentation of medical necessity. Recently OCA has received several questions from subscribers seeking clarification on the differences between, and correct coding for, antepartum fetal testing, including the contraction stress test (59020), fetal nonstress test (59025), and the fetal biophysical profile (76818).

These tests are common antepartum fetal assessments that belong to a group of tests used to identify a fetus at risk. According to Fundamentals of Gynecology and Obstetrics by Dale Russel Dunnihoo, MD, PhD (J.B. Lippincott Company, 1990), these tests are based on the premise that a fetus with a low fetal reserve (i.e., in poor condition) may be in danger of experiencing distress during the course of pregnancy and, particularly, during the course of labor. The status of the fetus can be evaluated by observing how it reacts during contractions (which produce stress). The physician monitors fetal vital signs, movement, fetal tone, amniotic fluid volume and the arterial blood flow.

These three tests require evidence of medical necessity. They would usually be ordered when a pregnancy is at increased risk for antepartum fetal demise.

1) Contraction Stress Test (CST)

Dunnihoo points out that the CST is based on the premise that, during a contraction, oxygenation of the fetus will decrease and create a situation of stress for the fetus. The obstetrician is interested in monitoring the fetal heart rate and seeing how quickly the fetus recovers from the stress of the contraction. If the fetus does not have much respiratory reserve it will experience late deceleration of the fetal heart rate (FHR). In patients who have a lower than normal volume of amniotic fluid, cord compression may occur during the contraction which causes a variable pattern of heart rate deceleration.

Coders should note that the contraction stress test (59020) is distinct and separate from other fetal testing. If it is performed before or after other tests, the coder must ensure that medical necessity is clearly documented. The contraction stress test is also a CPT starred procedure. According to CPT guidelines this means that it does not have a predetermined package of pre- or post-operative services. An evaluation and management (E/M) service for an established patient would not normally be reported in addition to this procedure, unless the documentation clearly noted that the E/M service was significant and separately identifiable. The separately identifiable E/M service would be denoted by adding a modifier -25 (significant, separately identifiable E/M service by same physician on the same day) to the E/M code.

2) The Nonstress Test (NST)

Unlike the CST, which monitors the fetus during the stress of contraction, the NST, according to both the ACOG bulletin and Dunnihoo, is merely the recording of the FHR over a period of time to determine whether there are any accelerations associated with the movements of the fetus. The patient is placed on her left side and the maternal blood pressure and an FHR tracing are obtained with an ultrasound transducer. The occurrence of at least two episodes of FHR accelerations within a 20-minute period that show an increase of 15 beats per minute and that last at least 15 seconds, is termed a reactive NST. A non-reactive test shows accelerations that do not meet the above criteria.

Coders should note that the NST (59025) often performed by the obstetrician in the office and can be coded by itself. But, when done as part of the biophysical profile only the biophysical profile code (76818) should be used.

3) The Fetal Biophysical Profile (BPP)

A more extensive approach to determining the status of the fetus is the use of the BPP (76818) and the biophysical profile score. This test includes an NST with the addition of four observations made by ultrasound. Together, the five components that are tested over a 30-minute period are:

Fetal breathing movements (episodes of fetal
breathing movements)

Fetal tone (extension and flexion of an extremity)

Fetal gross body movement (three or more discrete body-limb movements)

Amniotic fluid volume assessment

Reactive nonstress test

Each component is scored from 0 to +2 to determine the biophysical profile. A total score of 8-10 is considered normal.

The BPP is distinct and separate from the routine antepartum ultrasound (76805). Therefore, medical necessity must be shown by links to an appropriate diagnosis code. In general, according to Melanie Witt, RN, CPC, MA, program manager for ACOGs department of coding and nomenclature, you cannot code for both the NST and the BPP since the NST is included in the BPP. But in a situation where the obstetrician does a NST and then sends the patient to radiology for the BPP, both can be billed. However, the radiologist should add a modifier -52 (reduced services) if a medically necessary second NST is not performed.

Conditions Indicating Use of Antepartum Fetal Tests The following list contains some of the conditions that indicate the use of these tests, according to the American College of Obstetricians and Gynecologists (ACOG) Technical Bulletin No. 188. The associated diagnosis codes are: Decreased fetal movement 655.7X Hypertensive disorders 642.XX Diabetes mellitus (insulin treated) 648.0X Oligohydramnios (small amount of amniotic fluid) 658.0X Intrauterine growth retardation 656.5X Postdate pregnancy (42 weeks or more) 645.0X Isoimmunization (Rh factors) 656.1X Chronic renal disease 646.2X Systemic lupus erythematosus 648.9X Maternal cyanotic heart disease 648.6X Hemoglobinopathies (forms of abnormal hemoglobin in the blood) 648.2X Previously unexplained fetal demise V23.4 Multiple gestation with significantly discordant growth 651.XX with 656.5X or 656.6X Hyperthyroidism 648.1X