Newborn Drug Screening - Meconium and Umbilical Cord Tissue

Currently, no federal mandates or society guidelines exist that provide criteria for newborn drug testing. In general, medical care facilities and practitioners use either a universal or risk-based testing approach. Both options have benefits and drawbacks and may be influenced by local contexts (eg, laws, substance use prevalence, etc.).

Universal testing involves screening for neonatal drug exposure following each delivery. This approach is beneficial in that it prevents the use of biased testing protocols and may help to identify cases of neonatal drug exposure that would otherwise go untreated. It may be useful in areas where substance use prevalence is higher compared to the national average.  However, universal testing is more costly  and may expose more patients to legal and social risks. 

Risk-based testing involves screening for neonatal drug exposure in the presence of one or more objective risk factors, which can vary between facilities. In areas where substance use prevalence is low or below average, this approach may help to avoid excessive testing while still identifying affected neonates.  However, critics of a risk-based approach suggest that it enables discriminatory testing, especially in low-income and minority populations. It may also lead to missed treatment opportunities in unidentified cases of neonatal drug exposure. 

An approach that may overcome some of these limitations is to practice universal collection, wherein specimens are collected for every birth. Those specimens associated with risk factors could be tested right away, and those not associated could be stored for a period in which unexpected needs for testing could be exposed.

Regardless of the approach taken, the American College of Obstetricians and Gynecologists endorses informed consent and patient advocacy. 

Gabapentin is a widely used drug that, alone or with other drugs, has been linked to neonatal abstinence syndrome (NAS).   Notably, newborns coexposed to gabapentin and opioids during pregnancy have been shown to experience increased NAS severity and duration compared with those exposed only to opioids. When testing is indicated, consider a multidrug assay that includes gabapentin as an analyte.

See ARUP Laboratory Tests for a list of primary drugs detected for each assay. For a detailed discussion of the detection of gabapentin coexposure, see Patterns of Neonatal Co-Exposure to Gabapentin and Commonly Abused Drugs Observed in Umbilical Cord Tissue. 

Current data suggest little correlation between meconium or umbilical cord drug concentrations and neonatal exposure or outcomes.   For that reason, qualitative results are thought to be sufficient for determining in utero drug exposure. Exact drug concentrations within a sample may be informative when investigating patterns of drug exposure and unexpected results, the latter of which may be influenced by the established cutoff values for a particular test.

Several analytic factors (eg, cutoff values, the list of analytes targeted, etc.) can influence how the results of a newborn drug screen are reported. Interpretation of any newborn drug screen should also involve a complete review of the patient’s history, including prescriptions, drugs administered within a medical setting, home environment, and self-reported substance use.

For more on test interpretation, see Evaluation and Interpretation of Results.

Meconium is the traditional specimen for newborn drug testing, although its use may pose preanalytic challenges (eg, delayed or segmented collection). Umbilical cord tissue is easily collected at birth but has been found to contain lower drug concentrations than meconium.  For additional information about these specimens, see Preferred Specimen Types.

Urine, hair, and blood (including umbilical cord blood) tests offer different advantages, disadvantages, and windows of detection in newborn drug screening. The use of various specimen types is intended to complement the investigation of potential newborn drug exposure. For further discussion of these and other specimen types, refer to Detection of Drug-Exposed Newborns. 

The amount of time it takes to obtain meconium and umbilical cord test results may be influenced by many factors, including the timing of sample collection, the proximity of the laboratory performing the test, the method used for testing, and the possible need for reflex or confirmatory testing. Additionally, because meconium and umbilical cord tissue are solid specimens, processing them for testing requires more time and effort compared with the time and effort to process a liquid specimen used in rapid testing.

The expected time to obtain results should be weighed against other considerations (eg, test performance, included analytes, etc.) to determine the appropriate testing. When results are needed more promptly, single-step testing by a mass spectrometric method may be helpful. Because umbilical cord tissue can be collected immediately at birth, its use may also enable more rapid results. 

The clinical sensitivity of newborn drug testing is not well characterized. Results will only reflect the drugs an individual test is designed to detect, and findings may not match preanalytic expectations (ie, drugs may not always be detected, even when admissions of drug use are made).

In terms of analytic sensitivity, factors that may influence analyte detection in meconium and umbilical cord tissue testing include frequency and timing of drug use during pregnancy, sample quality, specimen processing, and test-specific cutoff concentrations for each drug. Analytic sensitivity also relates heavily to test method and cutoff concentrations. Notably, mass spectrometry (MS) is a highly sensitive and specific test method, and its use for confirmatory or primary testing minimizes the possibility of false results.

Because umbilical cord tissue and meconium drug screens are usually performed to support clinical and social management decisions rather than to facilitate law enforcement or criminal actions, chain of custody may not be required when testing. Consult local authorities and laws for more information.

When chain of custody may be a concern, consider testing that includes step-by-step specimen tracking. If chain of custody is not available or results seem otherwise questionable, comparing test results with patient history to identify expected substances (eg, prescriptions) alongside target analytes can reinforce the credibility of the test results.